BT6602/ Department of Biotechnology 2018-2019

DEPARTMENT OF BIOTECHNOLOGY

Faculty Name : Ms. K. Archana

Faculty Code : HTS 1407

Subject Name : IMMUNOLOGY

Subject Code : BT6602

Year & Semester : III & VI

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DEPARTMENT OF BIOTECHNOLOGY COURSE DETAILS

Faculty Name : Ms. K. Archana Faculty Code: HTS 1407 Subject Name: IMMUNOLOGY Subject Code: BT6602 Department: Biotechnology Year & Semester: III & VI

COURSE OUTCOMES On completion of this course, the students will be able to Knowledge CO No Course Outcomes Level C314.1 Understand the concepts on and immune responses. K2 C314.2 Discuss the structure and functions of . K2

C314.3 Describe the to various pathogens. K2

C314.4 Understand therapeutic/diagnostic molecules. K2 C314.5 Differentiate the types of tumour, and hypersensivity reactions. K2

Mapping of Course Outcomes with Program Outcomes and Program Specific Outcomes

BT6602 PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12 PSO1 PSO2 PSO3 PSO4 C314.1 3 ------2 3 - - - - C314.2 3 ------2 3 - - - - C314.3 3 - - - - 3 3 - - - 2 3 - - 3 - C314.4 3 - - - - 3 3 - - - 3 2 - - 3 - C314.5 3 - - - - 3 3 - - - 3 3 - - 3 -

BT6602 PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12 PSO1 PSO2 PSO3 PSO4 C314 3 - - - - 3 3 - - - 2 3 - - 3 -

K1 – Remember; K2 – Understand; K3 – Apply; K4 – Analyze; K5 – Evaluate; K6 - Create

Mapping Relevancy 1: Slight (Low) 2: Moderate (Medium) 3 Substantial (High) - : No correlation 2 BT6602/Immunology Department of Biotechnology 2018-2019

UNIT-I INTRODUCTION Part-A 1. What is immunology? Immunology is a branch of biology it is concerned with immunity. It is resistance of living organisms of infection of microorganisms. 2. Define (2011, 2012) A substance that can produce a specific immune response when it is introduced into the tissues of an animal and that can react specifically with the products of that immune response namely antibodies or sensitized cells is known as an antigen. 3. What is innate immunity? (2008) All living organisms are naturally gifted with the resistance to certain infections from birth and this natural defense mechanism is known as innate immunity or native immunity 4. What is non-innate immunity? (2007, 2011) The resistance developed by man during his life is known as acquired immunity or adaptive immunity 5. What is primary immune response (May 2017) The primary immune response occurs when an antigen comes in contact to the immune system for the first time. During this time the immune system has to learn to recognize antigen and how to make against it and eventually produce memory . 6. What are Adjuvants (May 2017) An adjuvant is a pharmacological or immunological agent that modifies the effect of other agents. Adjuvants may be added to a vaccine to modify the immune response by boosting it such as to give a higher amount of antibodies and a longer-lasting protection, thus minimizing the amount of injected foreign material. Adjuvants may also be used to enhance the efficacy of a vaccine by helping to modify the immune response to particular types of immune system cells: for example, by activating T cells instead of antibody-secreting B cells depending on the purpose of the vaccine. 7. What is opsonisation? (2007, May 2016) It is by which a pathogen is marked for ingestion and destruction by a . Opsonization involves the binding of an , i.e., antibody, to a receptor on the pathogen's cell membrane. After opsonin binds to the membrane, are attracted to the pathogen. The Fa and Fb portion of the antibody binds to the antigen, whereas the Fc portion of the antibody binds to an on the phagocyte, facilitating . The receptor-opsoin complex can also create byproducts like C3b and C4b which are important components of the . These components are deposited on the cell surface of the pathogen and aid in its destruction 8. What is macropohage The are the cells of the mononuclear phagocytic system which was originally called the reticuloendothelial system, which includes kupffer cells (liver), osteoblasis (bone) etc. 9. What is natural killer cells (2007) These are non-phagocytic lymphoid cells having large granules. Hence, these cells are also known as large granular lymphocytes. These cells show natural cytotoxicity and they can kill a range of tumor cells and cells infected with any type of viruses with out any antigen specificity 10. What is an adaptive or acquired immune response?(2009, 2010, 2012) The resistance developed by man during his life is known as acquired immunity or adaptive immunity 11. What is Immunity mediates by antibodies produced in the humors or body fluids such as plasma or lymph is known as humoral immunity 12. What is cell mediated immunity The immunity produced by the sensitized lymphocytes is called cell-mediated immunity. 13. What are secondary lymphoid organs? (2008, 2009, 2011) Secondary lymphoid organs are the organs where lymphocytes encounters the antigen and sharpen up the immune response by clonal expansion and affinity maturation; and provide a home for lymphocytes,

3 BT6602/Immunology Department of Biotechnology 2018-2019 where they can be available when they are needed. Eg. For secondary lymphoid organs is spleen, lymph node, MALT, GALT, payer patches 14. What is MALT? (2007) The mucosa-associated lymphoid tissue (MALT) (also called mucosa-associated lymphatic tissue) is the diffuse system of small concentrations of lymphoid tissue found in various sites of the body, such as the gastrointestinal tract, thyroid, breast, lung, salivary glands, eye, and skin. MALT is populated by lymphocytes such as T cells and B cells, as well as plasma cells and macrophages, each of which is well situated to encounter passing through the mucosal epithelium. 15. What is The immunity that non immune individual acquired by receiving antibodies or sensitized white blood cells from another immune individual is known as passive immunity. 16. What is lymphocytes Lymphocytes are the chief constituents of the lymphoid tissues. They produced by the primary lymphoid organs namely thymus (T lymphocytes) and bone marrow or bursa (B lymphocytes). They are cells which are spherical or ovoid in shape about 7-12 µm in diameter, with a large round nucleus, usually indented into a kidney shape when observed under the electron microscope. The chromatin in the nucleus is densely packed and stained intensely blue with most routinely used stains such as Giemsa or Wright. 17. What is Langerhans cells They are antigen presenting cell present in the skin. From the skin they can migrate into the spleen and lymph nodes. They contain class I and II MHC molecules, Fc and C3 receptors. 18. What is dendritic cells They are antigen presenting cell present in the spleen and lymph nodes. They contain Fc receptors and class II MHC molecules. 19. What is mast cells (May2016) These are large tissue cells with large tissue cells with basophilic granules in the cytoplasm. Mast cells of the sessile are similar in appearance and function to the of blood. Basophils are circulating in the blood whereas the mast cells are sessile and present throughout the body. These cells are about 10-30µm in diameter and they have a polymorphous nucleus.. There are 2 types of mast cells- Mucosal mast cell and connective tissue mast cells. 20. How IFN act against viruses (May 2014) A glyco-protein secreted by cells when infected with a virus. It triggers a cellular reaction that halts synthesis of viral nucleic acid and consequently disrupts viral life cycle. It also inhibits the proliferation of normal and transformed cells. 21. What is antigenicity? The ability of an antigen to produce an immune response and react with the products is known as antigenicity 22. What is immunogenicity? The ability of a material to induce an immune response is referred as immunogenicity and such material are known as . 23. What is immunological memory The remembering of the primary immune response by the defense system is called immunological memory. 24. What is Avidity (2008, June 2014) The strength of binding between antigen and antibody 25. Define ? (2007, 2011, 2013) It is a substance that can combine with an antibody but cannot initiate an immune response (not immunogenic) by itself unless it is bound to a carrier before introduction into the body 26. What is sequestered antigens Certain antigens remain in secluded places. They are not accessible to the immune system. These antigens are called sequestered antigens or hidden antigens. 27. What is Foetal antigens The differentiated cell undergoes dedifferentiation to become tumour cells. As a result of dedifferentiation, the adult cell becomes an embryonic cell. The foetal antigens include α fetoprotein in hepatic carcinoma and crcino embryonic antigen in cancer of the intestine. 4 BT6602/Immunology Department of Biotechnology 2018-2019

28. What is Neoantigens They are altered or modified antigens. These antigens are modified by physical against (irradiation) or chemical agents (drugs) or microbial agents as intracellular viruses. The altered antigens are no longer considered by the immune system as self antigens. Hence the altered antigens provoke an autoimmune response. 29. Define viral antigens When tumour is induced by virus, the antigens of the infecting virus appears on the surface of tumour cells. These antigens are called viral specific antigens or V antigens. 30. What is chemical induced antigens The tumour cells induced by chemicals contain a new type of antigen called tumour specific transplantation antigens 31. What is Idiotypic antigens They are unique antigens. The tumour cells, induced by different chemicals, produce different types of idotypic antigens of the surface. 32. What anti-idiotypic antibodies? (2008) It is an antibody that binds to the antigen-combining site of another antibody either suppressing or enhancing the immune response 33. What are commensals? (2007) This refers to ‘Eating at the same table’. In neutral situation where host and bacteria live together, but have no effect on each others life cycle. Either positive or negative this is called commensalisms. 34. Define polyclonal antibody (2009, 2010) (or antisera) are antibodies that are obtained from different resources. They are a combination of immunoglobulin molecules secreted against a specific antigen, each identifying a different . 35. What is theory (2015, May2016) Clonal selection theory is a scientific theory in immunology that explains the functions of cells (lymphocytes) of the immune system in response to specific antigens invading the body.  Each bears a single type of receptor with a unique specificity (by V(D)J recombination).  Receptor occupation is required for cell activation.  The differentiated effector cells derived from an activated lymphocyte will bear receptors of identical specificity as the parental cell.  Those lymphocytes bearing receptors for self molecules will be deleted at an early stage. Part-B 1. Classify immunity and describe acquired immunity (May 2016) 2. Explain in detail about the cells of the immune system and clonal selection theory. (2011, 2012) 3. Explain the structure and function of primary lymphoid organs (May 2014) 4. Describe the structure and function of the lymphoid organs like lymph and bone marrow with suitable diagrams (2009, 2012) 5. Write a note on Adjuvants (2011, May 2014) 6. Describe in detail secondary lymphoid organs (2007, 2008, May 2017) 7. Describe Innate immunity with suitable example 8. Write a detail account on Spleen 9. Describe in detail about thymus and Lymph node(2012, 2015) 10. Describe the anatomy and immune function of payer patches 11. Explain the types of antigen with suitable example 12. Write a detail account on the chemical and molecular nature of antigen (2015) 13. Write a detail account on classification of Antigens 14. Explain the principle and applications of monoclonal antibodies by citing examples. (2008, 2009, 2007, 2011, 2013, May 2016, May 2017)

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1. Explain in detail the primary lymphoid organs with a suitable diagrams Thymus: The thymus is the site of T-cell development and maturation. It is a flat, bilobed organ situated above the heart. Each lobe is surrounded by a capsule and is divided into lobules, which are separated from each other by strands of connective tissue called trabeculae. Each lobule is organized into two compartments: the outer compartment, or cortex, is densely packed with immature T cells, called , whereas the inner compartment, or medulla, is sparsely populated with thymocytes. Both the cortex and medulla of the thymus are crisscrossed by a three-dimensional stromal- cell network composed of epithelial cells, dendritic cells, and macrophages, which make up the framework of the organ and contribute to the growth and maturation of thymocytes. Many of these stromal cells interact physically with the developing thymocytes (Figure 2- 14). Some thymic epithelial cells in the outer cortex, called nurse cells, have long membrane extensions that surround as many as 50 thymocytes, forming large multicellular complexes. Other cortical epithelial cells have long interconnecting cytoplasmic extensions that form a network and have been shown to interact with numerous thymocytes as they traverse the cortex. The function of the thymus is to generate and select a repertoire of T cells that will protect the body from infection. As thymocytes develop, an enormous diversity of T-cell receptors is generated by a random process) that produces some T cells with receptors capable of recognizing antigen-MHC complexes

Bone Marrow: In humans and mice, bone marrow is the site of B-cell origin and development. Arising from lymphoid progenitors, immature B cells proliferate and differentiate within the bone marrow, and stromal cells within the bone marrow interact directly with the B cells and secrete various that are required for development. Like thymic selection during Tcell maturation, a selection process within the bone marrow eliminates B cells with self- reactive antibody receptors. Bone marrow is not the site of B-cell development in all species. In birds, a lymphoid organ called the bursa of Fabricius, a lymphoid In humans and mice, bone marrow is the site of B-cell origin and development. Arising from lymphoid progenitors, immature B cells proliferate and differentiate within the bone marrow, and stromal cells within the bone marrow interact directly with the B cells and secrete various cytokines that are required for development. Like thymic selection during Tcell maturation, a selection process within the bone marrow eliminates B cells with self- reactive antibody receptors. Bone marrow is not the site of B-cell development in all 6 BT6602/Immunology Department of Biotechnology 2018-2019

species. In birds, a lymphoid organ called the bursa of Fabricius, a lymphoid tissue associated with the gut, is the primary site of B-cell maturation. In mammals such as primates and rodents, there is no bursa and no single counterpart to it as a primary lymphoid organ.

2. Discuss the production of polyclonal antibodies by the immune system with suitable sketches These antibodies are typically produced by inoculation of a suitable mammal, such as a mouse, rabbit or goat. Larger mammals are often preferred as the amount of serum that can be collected is greater. An antigen is injected into the mammal. This induces the B- lymphocytes to produce IgG immunoglobulins specific for the antigen. This polyclonal IgG is purified from the mammal’s serum. By contrast, monoclonal antibodies are derived from a single cell line. Many methodologies exist for polyclonal antibody production in laboratory animals. Institutional guidelines governing animal use and procedures relating to these methodologies are generally oriented around humane considerations and appropriate conduct for adjuvant (agents which modify the effect of other agents while having few if any direct effects when given by themselves) use. This includes adjuvant selection, routes and sites of administration, injection volumes per site and number of sites per animal. Institutional policies generally include allowable volumes of blood per collection and safety precautions including appropriate restraint and sedation or anesthesia of animals for injury prevention to animals or personnel. The primary goal of antibody production in laboratory animals is to obtain high titer, high affinity antisera for use in experimentation or diagnostic tests. Adjuvants are used to improve or enhance an immune response to antigens. Most adjuvants provide for an injection site, antigen depot which allows for a slow release of antigen into draining lymph nodes. Many adjuvants also contain or act directly as: surfactants which promote concentration of protein antigens molecules over a large surface area, and immunostimulatory molecules or properties. Adjuvants are generally used with soluble protein antigens to increase antibody titers and induce a prolonged response with accompanying memory. Such antigens by themselves are generally poor immunogens. Most complex protein antigens induce multiple B-cell clones during the immune response, thus, the response is polyclonal. Immune responses to non-protein antigens are generally poorly or enhanced by adjuvants and there is no system memory. Antibodies are currently also being produced from isolation of human B-lymphocytes to produce specific recombinant polyclonal antibodies. The biotechnology company, Symphogen, produces this type of antibody for therapeutic applications. They are the first research company to develop recombinant polyclonal antibody drugs to reach phase two trials. This production prevents viral and prion transmission. 3. Classify immunity and describe acquired immunity Acquired (adaptive or specific) immunity is not present at birth. It is learned. As a person’s immune system encounters foreign substances (antigens), the components of acquired immunity learn the best way to attack each antigen and begin to develop a memory for that antigen. Acquired immunity is also called specific immunity because it tailors its attack to a specific antigen previously encountered. Its hallmarks are its ability to learn, adapt, and remember.

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Acquired immunity takes time to develop after first exposure to a new antigen. However afterward, the antigen is remembered, and subsequent responses to that antigen are quicker and more effective than those that occurred after the first exposure. The white blood cells responsible for acquired immunity are Lymphocytes (T cells and B cells) a. Typically, an acquired immune response begins when antibodies, produced by B cells (B lymphocytes), encounter an antigen. b. Other participants in acquired immunity are Dendritic cells (see Acquired Immunity : Dendritic Cells) Cytokines (see Innate Immunity : Cytokines) The complement system (which enhances the effectiveness of antibodies—see Innate Immunity : Complement System) Lymphocytes enable the body to remember antigens and to distinguish self from harmful nonself (including viruses and bacteria). Lymphocytes circulate in the bloodstream and lymphatic system and move into tissues as needed. The immune system can remember every antigen encountered because after an encounter, some lymphocytes develop into memory cells. These cells live a long time—for years or even decades. When these cells encounter an antigen for the second time, they recognize it immediately and respond quickly, vigorously, and specifically to that particular antigen. This specific immune response is the reason that people do not contract chickenpox or measles more than once and that vaccination can prevent certain disorders. Lymphocytes may be T cells or B cells. T cells are produced in the thymus. They can potentially recognize an almost limitless number of different antigens. To avoid attacking the body's own tissues, they need to learn how to distinguish self from nonself antigens. Normally, only the T cells that ignore the body's own antigens (self-antigens) are allowed to mature and leave the thymus. T cells are produced in the thymus. They can potentially recognize an almost limitless number of different antigens. To avoid attacking the body's own tissues, they need to learn how to distinguish self from nonself antigens. Normally, only the T cells that ignore the body's own antigens (self-antigens) are allowed to mature and leave the thymus. Mature T cells are stored in secondary lymphoid organs (lymph nodes, spleen, tonsils, appendix, and Peyer patches in the small intestine). These cells circulate in the bloodstream and the lymphatic system. After they first encounter an infected or abnormal cell, they are activated and search for those particular cells. B cells: B cells are formed in the bone marrow. B cells have particular sites (receptors) on their surface where antigens can attach. B cells can learn to recognize an almost limitless number of different antigens. The B-cell response to antigens has two stages: Primary immune response: When B cells first encounter an antigen, the antigen attaches to a receptor, stimulating the B cells. Some B cells change into memory cells, which remember that specific antigen, and others change into plasma cells. Helper T cells help B cells in this process. Plasma cells produce antibodies that are specific to the antigen that stimulated their production. After the first encounter with an antigen, production of enough of the specific antibody takes several days. Thus, the primary immune response is slow. Secondary immune response: But thereafter, whenever B cells encounter the antigen again, memory B cells very rapidly recognize the antigen, multiply, change into plasma cells, and produce antibodies. This response is quick and very effective. Although the main function of B cells is to produce antibodies, they can also present antigen to T cells.

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4. Write in detail about the production and application of Monoclonal antibodies. Most antigens offer multiple and therefore induce proliferation and differentiation of a variety of B-cell clones, each derived from a B cell that recognizes a particular epitope. The resulting serum antibodies are heterogeneous, comprising a mixture of antibodies, each specific for one epitope (Figure 4-21). Such a polyclonal antibody response facilitates the localization, phagocytosis, and complement-mediated lysis of antigen; it thus has clear advantages for the organism in vivo. Unfortunately, the antibody heterogeneity that increases immune protection in vivo often reduces the efficacy of an antiserum for various in vitro uses. For most research, diagnostic, and therapeutic purposes, monoclonal antibodies, derived from a single clone and thus specific for a single epitope, are preferable. Direct biochemical purification of a from a polyclonal antibody preparation is not feasible. In 1975, Georges Köhler and Cesar Milstein devised a method for preparing monoclonal antibody, which quickly became one of immunology’s key technologies. By fusing a normal activated, antibody-producing B cell with a myeloma cell (a cancerous ), they were able to generate a hybrid cell, called a hybridoma, that possessed the immortalgrowth properties of the myeloma cell and secreted the antibody produced by the B cell. The resulting clones of hybridoma cells, which secrete large quantities of monoclonal antibody, can be cultured indefinitely.

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UNIT-II CELLULAR RESPONSES Part-A 1. How do class I MHC molecules differ from class-II molecules (2015, May 2017). MHC class-I molecules- Class I MHC molecules bind peptides generated mainly from degradation of cytosolic proteins by the proteasome. The function of the class I MHC is to display the antigenic peptide to cytotoxic T cells (CTLs). MHC class-II molecules - the antigens presented by class II peptides are derived from extracellular proteins (not cytosolic as in class I); hence, the MHC class II-dependent pathway of is called the endocytic or exogenous pathway. Loading of a MHC class II molecule occurs by phagocytosis; extracellular proteins are endocytosed, digested in lysosomes, and the resulting epitopic peptide fragments are loaded onto MHC class II molecules prior to their migration to the cell surface. 2. Define Tolerance (May 2017) When an antigen fails to stimulate an immune response, or fails to activate enough amount of lymphocytes can induce a state of immunological unresponsiveness is called tolerance 3. Define Epitopes The part of the antigen with which the antibody reacts is known as the antigenic determinant or epitope. Usually, the epitopes are found on the surface of the antigen but denaturation and unfolding of the antigen has revealed that the antigen has some hidden epitopes in addition to the functional surface epitopes. The number of antigenic determinant s per molecule of antigen is referred to as the valency. 4. Define The portion of the antibody molecule that binds to the epitope is called the 5. What is Fab Fragment, antigen binding is the segment of the antibody containing paratope. It is located at the extremity of two limbs of the Y. it consists of a light chain and part of the heavy chain. Fab fragment can be separated by enzymatic digestion 6. What is Fc Fragment crystalline is a fragment of antibody responsible for the binding of antibody and complement to antibody receptors of cells. 7. How will you identify a human B cell? (2009) B cell are identified by the presence of the CD 40, B cell receptors and interleukins 8. What is SRID? (2009) Single Radial Immunodiffusion technique (SRID) is a technique for quantitating soluble proteins that involves placing the solution to be measured into a well cut into an agar or agarose gel containing antiserum specific for the protein. As the solution to be measured diffuses out of the well, it complexes with the antiserum and forms a ring, the size of which is proportional to the quantity of soluble protein in the well. 9. What is meant by antibody diversity? (2007) The phenomenon of immense variability characteristic of antibodies, which enables the immune system to react specifically against the essentially unlimited kinds of antigens it encounters. Antibody diversity is accounted for by three main theories: 1) the germ line theory, which holds that each antibody- producing cell has genes coding for all possible antibody specificities, but expresses only the one stimulated by antigen; 2) the somatic mutation theory, which holds that antibody-producing cells contain only a few genes, which produce antibody diversity by mutation; and 3) the gene rearrangement theory, which holds that antibody diversity is generated by the rearrangement of variable region gene segments during the differentiation of the antibody-producing cells. 10. What is immunoglobulin? Immunoglobulins are a group of glycoproteins present in the serum and tissue fluids of all vertebrate species. These are the products of plasma cells which have developed from the B lymphocytes. They have antibody activity i.e. when an immunoglobulin reacts with a specific antigen it is called an antibody. 11. Mention the biological properties of Ig G It is the only immunoglobulin that crosses the human placenta and thus offers a passive protection to the newborn for about 6-9 months. It activates the classical complement pathway during antigen antibody reactions. It neutralizes toxins and viruses. It binds to the bacteria and opsonises them, there by enhance the phagocytosis and elimination. 10 BT6602/Immunology Department of Biotechnology 2018-2019

12. Mention the biological properties of Ig A It inhibits the adherence of microbes to the mucosa of the respiratory, gastro intestinal and urinogenital tracts there by prevent them from colonizing and invading the different organs of these tracts. It activates the alternate complement pathway there by neutralizes local toxins, promote phagocytosis and activate bacteriolytic activity. It is present in the colostrum protects the baby from intestinal pathogens. 13. Mention the biological properties of Ig M It is the first antibody to appear in the primary immune response. Most antural antibodies such as anti- A and anti- B are of the Ig M class. It has a multiple antigen binding sites (5-10) and has a high function affinity for multivalent antigens. It also shows properties such as opsonisation, complement fixation agglutination, cytolysis etc. 14. Define Antigen presenting cells (2010, 2012, 2013) These are non lymphocytic cells, whose function is to carry antigens and present them to the immunocompetent lymphocytes which are located in the secondary lymphoid organs 15. What are non-professional APC (May 2014) A non-professional APC does not constitutively express the Major Complex class II (MHC class II) proteins required for interaction with naive T cells; these are expressed only upon stimulation of the non-professional APC by certain cytokines such asIFN-γ. Non-professional APCs include: Fibroblasts (skin), Thymic epithelial cells, Thyroid epithelial cells, Glial cells (brain), Pancreatic beta cells, Vascular endothelial cells 16. Mention the biological properties of Ig E It protects children with worm infestation. The protective function is either by acting directly on the parasites or by producing vasoactive amines (histamines). 17. What is monoclonal antibody (2011) It is a single ype of antibody, produced by hybridoma cell line, and directed against an antigenic determinant. The hybridoma cell line is formed by the fusion of lymphocyte cell and a myeleoma cell. 18. How will you identify a using a monoclonal antibody? (2007) Macrophage can be identified by specific expression of a number of proteins including CD14, CD11b, F4/80 (mice)/EMR1 (human), Lysozyme M, MAC-1/MAC-3 and CD68. Monoclonal antibodies can be prepared against this marker and identified using immunohistochemical stainings. 19. What are receptors (2015, May 2016) The T cell receptor or TCR is a molecule found on the surface of T lymphocytes (or T cells) that is responsible for recognizingantigens bound to major histocompatibility complex (MHC) molecules. The TCR is composed of two different protein chains (that is, it is a heterodimer). In humans 95% of T cells the TCR consists of an alpha (α) and beta (β) chain, whereas in 5% of T cells the TCR consists of gamma and delta (γ/δ) chains. This ratio changes duringontogeny and in diseased states as well as in different species.When the TCR engages with antigenic peptide and MHC (peptide/MHC), the T lymphocyte is activated through signal transduction, of biochemical events mediated by associated enzymes, co- receptors, specialized adaptor molecules, and activated or released transcription factors that is, a series. 20. Mention the types of T-cells. (2008) , T cytotoxic cell, T delayed type hypersensitive cell 21. Define complement (2015) It refers to a group of large thermolabile enzymatic proteins found in the serum and body fluids and it completes like antigen- antibody reaction, lysis and phagocytosis. 22. How complements are activated? The complement components are made active by certain substances called activating substances or activating agents. They include antigen-antibody complexes, gram negative bacteria, animal viruses aggregated antibodies like Ig G or Ig A, endotoxin, yeast, etc. when one component is activated other components are triggered in a sequence in a cascade pattern to bring about a biological activity such as lysis, phagocytosis, etc. 23. What is MHC (2011, Dec 2013) Major histocompatibility complex refers to a cluster of genes responsible for immune response, transplantation antigens and proteins of the complement system. 24. What is H-2 complex

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The major histocompatibility complex of mouse is called H-2 complex. It is a cluster of genes responsible for the production of antigens located on the membrane of nucleated cells and complement components. This complex is located in the short arm of the chromosome number 17. 25. What is cross reactive antigens It is one which is capable of binding to antibody produced in response to a different antigen. This is due to sharing of determinants by the two antigens or because the antigenic determinant of the two, although not identical, are closely enough related stereochemically to combine with antibody against any one of them. Eg. Heterophile antigen. Part-B 1. Discuss the structure and functions of antibody (Ig G) (2007, 2011, 2012, May 2016, May 2017) 2. Explain B cell activation and Proliferation (May 2015) 3. How antigens are processed and presented by antigen presenting cells (2013, May 2016) 4. Write a detail account on the types of antibodies 5. Explain how a human B cell is triggered to produce antibodies (2009) 6. Discuss the development of human T cells and how they matures functional cells (2009, May 2017) 7. Explain in detail about T and B lymphocytes. (2007) 8. Discuss the mechanisms of macrophage activation (2008, 2007) 9. Write a detail account on antigen- antibody reaction. (2007) 10. b) Write a detail account on precipitation 11. Explain the overview of TCR mediated signaling 12. Write a detail account on MHCI and MHC II (May 2014) 13. Explain two pathways of antigen processing and presentation (May 2014, 2015) 1.Explain the antigen processing and presentation by APC. Add note on function of CMI Cells that display peptides associated with class I MHC molecules to CD8 TC cells are referred to as target cells; cells that display peptides associated with class II MHC molecules to CD4 TH cells are called antigen-presenting cells (APCs). Three cell types are classified as professional antigen-presenting cells: dendritic cells, macrophages, and B lymphocytes. Evidence for Two Processing and Presentation Pathways The immune system uses two different pathways to eliminate intracellular and extracellular antigens Cytosolic pathway Endocytic pathway Endogenous antigens (those generated within the cell) are processed in the cytosolic pathway and presented on the membrane with class I MHC molecules; Exogenous antigens (those taken up by endocytosis) are processed in the endocytic pathway and presented on the membrane with class II MHC molecules

Exogenous Antigens: The Endocytic Pathway Antigen-presenting cells can internalize antigen by phagocytosis, endocytosis, or both.

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Macrophages internalize antigen by both processes, whereas most other APCs are not phagocytic or are poorly phagocytic and therefore internalize exogenous antigen only by endocytosis (either receptor-mediated endocytosis or pinocytosis). B cells, for example, internalize antigen very effectively by receptor-mediated endocytosis using antigen-specific membrane antibody as the receptor. Peptides Are Generated from Internalized Molecules in Endocytic Vesicles Once an antigen is internalized, it is degraded into peptides within compartments of the endocytic processing pathway. Internalized antigen takes 1–3 h to transverse the endocytic pathway and appear at the cell surface in the form of peptide–class II MHC complexes. The endocytic pathway appears to involve Three increasingly acidic compartments: early endosomes (pH 6.0–6.5); late endosomes, (pH 5.0–6.0); lysosomes (pH 4.5–5.0). Internalized antigen moves from early to late endosomes and finally to lysosomes, encountering hydrolytic enzymes and a lower pH in each compartment Lysosomes, contain a unique collection of more than 40 acid-dependent hydrolases, including proteases, nucleases, glycosidases, lipases, phospholipases, and phosphatases. Within the compartments of the endocytic pathway, antigen is degraded into oligopeptides of about 13–18 residues, which bind to class II MHC molecules. Because the hydrolytic enzymes are optimally active under acidic conditions (low pH), antigen processing can be inhibited by chemical agents that increase the pH of the compartments (e.g., chloroquine) as well as by protease inhibitors (e.g., leupeptin)

2.Elucidate the structure and functions of immunoglobulins. Antibodies Are Heterodimers, Four peptide chains, Two identical light (L) chains (25,000 M.W), Two identical heavy (H) chains (50,000 or more), Two types of light chains namely Kappa and lambda. Based on the presence of light chain Ig are of two types namely K type and L type. Approximately 60% of the serum Ig moleucles are k type while only 40% are L type, 5 Different types of heavy chains designated as α, , µ,  and ɛ. Based on the heavy chain Ig are designated as IgG, IgA, Ig M, Ig D and Ig E. Heavy chain has a central flexible region know as hinge at which they are linked with one another by 1 to 13 inter chain disulfide bonds deponding on the the class of Ig. Each light chain is bound to a heavy chain by a single interchain disulfide bond and by such noncovalent interactions as salt linkages, hydrogen bonds, and hydrophobic bonds, to form a heterodimer (H-L). Similar non-covalent interactions and disulfide bridges link the two identical heavy and light (H-L) chain combinations to each other to form the basic four-chain (H-L)2 antibody structure, a dimer of dimers. Each of the light and heavy chains have two terminal ends called the N terminal end or amino terminal end and the C terminal end or carboxy terminal end. Each light chain has about 214 amino acids and each heavy chain about twice as long as the light chain. Human may be considered as a typical example of the basic antibody structure. Half the Light chain near to the N terminal is Variable light region (VL) and other half near to the C terminal is constant light Region(CL). One quarter of heavy chain towards N terminal is Variable Heavy chain Region (VH) and Remaining 3 quarter towards C terminal is Constant region (CH1, CH2, and CH3). V regions called complementarity-determining regions (CDRs), and it is these CDRs, on both light and heavy chains, that constitute the antigen binding site of the antibody molecule. Each light chain has 2 intrachain disulfide bonds one in VL and another in VH. Being glycoproteins, the immunoglobulin have carbohydrate moiety in them and carbohydrate is usually associated with the constant region of the heavy chain. The sugar moiety found in the Ig are fucose, glatose, mannose, glucosamine and sialic acid. Carbohydrates range from 2 to 3 % for IgG to as high as 14 % for Ig D 13 BT6602/Immunology Department of Biotechnology 2018-2019

14.

3.Explain the principle of production and the diagnostic, theraputical application of monoclonal antibodies Most antigens offer multiple epitopes and therefore induce proliferation and differentiation of a variety of B-cell clones, each derived from a B cell that recognizes a particular epitope. The resulting serum antibodies are heterogeneous, comprising a mixture of antibodies, each specific for one epitope (Figure 4-21). Such a polyclonal antibody response facilitates the localization, phagocytosis, and complement-mediated lysis of antigen; it thus has clear advantages for the organism in vivo. Unfortunately, the antibody heterogeneity that increases immune protection in vivo often reduces the efficacy of an antiserum for various in vitro uses. For most research, diagnostic, and therapeutic purposes, monoclonal antibodies, derived from a single clone and thus specific for a single epitope, are preferable. Direct biochemical purification of a monoclonal antibody from a polyclonal antibody preparation is not feasible. In 1975, Georges Köhler and Cesar Milstein devised a method for preparing monoclonal antibody, which quickly became one of immunology’s key technologies. By fusing a normal activated, antibody-producing B cell with a myeloma cell (a cancerous plasma cell), they were able to generate a hybrid cell, called a hybridoma, that possessed the immortalgrowth properties of the myeloma cell and secreted the antibody produced by the B cell. The resulting clones of hybridoma cells, which secrete large quantities of monoclonal antibody, can be cultured indefinitely.

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4.What are antigen presenting cells? Explain the processing and presentation of bacterial antigens by APC Cells that display peptides associated with class I MHC molecules to CD8 TC cells are referred to as target cells; cells that display peptides associated with class II MHC molecules to CD4 TH cells are called antigen-presenting cells (APCs). Three cell types are classified as professional antigen-presenting cells: dendritic cells, macrophages, and B lymphocytes. Evidence for Two Processing and Presentation Pathways The immune system uses two different pathways to eliminate intracellular and extracellular antigens Cytosolic pathway Endocytic pathway Endogenous antigens (those generated within the cell) are processed in the cytosolic pathway and presented on the membrane with class I MHC molecules; Exogenous antigens (those taken up by endocytosis) are processed in the endocytic pathway and presented on the membrane with class II MHC molecules

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Exogenous Antigens: The Endocytic Pathway Antigen-presenting cells can internalize antigen by phagocytosis, endocytosis, or both. Macrophages internalize antigen by both processes, whereas most other APCs are not phagocytic or are poorly phagocytic and therefore internalize exogenous antigen only by endocytosis (either receptor-mediated endocytosis or pinocytosis). B cells, for example, internalize antigen very effectively by receptor-mediated endocytosis using antigen-specific membrane antibody as the receptor. Peptides Are Generated from Internalized Molecules in Endocytic Vesicles Once an antigen is internalized, it is degraded into peptides within compartments of the endocytic processing pathway. Internalized antigen takes 1–3 h to transverse the endocytic pathway and appear at the cell surface in the form of peptide–class II MHC complexes. The endocytic pathway appears to involve Three increasingly acidic compartments: early endosomes (pH 6.0–6.5); late endosomes, (pH 5.0–6.0); lysosomes (pH 4.5–5.0). Internalized antigen moves from early to late endosomes and finally to lysosomes, encountering hydrolytic enzymes and a lower pH in each compartment Lysosomes, contain a unique collection of more than 40 acid-dependent hydrolases, including proteases, nucleases, glycosidases, lipases, phospholipases, and phosphatases. Within the compartments of the endocytic pathway, antigen is degraded into oligopeptides of about 13–18 residues, which bind to class II MHC molecules. Because the hydrolytic enzymes are optimally active under acidic conditions (low pH), antigen processing can be inhibited by chemical agents that increase the pH of the compartments (e.g., chloroquine) as well as by protease inhibitors (e.g., leupeptin)

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UNIT-III INFECTION AND IMMUNITY Part-A 1. Define tolerance (2007, 2009, 2011, 2012, May2016, May 2017) It is the process by which the immune system does not attack an antigen. It can be either 'natural' or 'self tolerance', where the body does not mount an immune response to self antigens, or 'induced tolerance', where tolerance to external antigens can be created by manipulating the immune system. It occurs in three forms: , and acquired tolerance. 2. How Virus Evade immune response (2015)  Viruses have evolved a plethora of mechanisms to inhibit every step of the innate and adaptive immune responses.  Viruses avoid detection by pattern recognition receptors, T cell receptors and antibodies by modifying the ligands for these receptors.  Different viruses target every stage of antigen processing and presentation by MHC molecules, thus inhibiting recognition by T cells.  Interferons, cytokines and chemokines are mimicked or blocked by viral proteins to prevent the efficient development of an immune response.  Through repression of their replication, viruses are able to enter latency and remain dormant inside the cell, remaining undetectable. 3. Write a short note on extravasation Extavasation is the process in wihich the lymphocytes migrates towards the site of infection and extravasate by a similar process. The process of extravasation can be divided into four sequential steps: (1) rolling, (2) activation by chemoattractant stimulus, 3) arrest and adhesion, and (4) transendothelial migration

4. Compare the properties of T and B lymphocytes B and T lymphocytes develop in primary lymphoid organs. B lymphocyte synthesize and secretes antibodies, T lymphocytes participates in cell mediated immunity, and they help B cell make antibodies. They also participate in various regulatory aspects of the immune response by releasing soluble factors termed lymphokines. 5. Describe the biological function of IL-2 Activation of T and B cell by antigen results in secretion of specific glycoprotein like IL-2. It has profound effects on the proliferation and differentiation of T as well as B cells. 6. Define passive agglutination by the administration of performed antibody in to a non immune individual 7. Describe the mechanism of phagocytosis Engulf of a particle or a microorganism by leukocytes. The process of phagocytosis includes the chemotaxis, attachment, ingestion, intracellular killing and digestion. 8. Differentiate between isograft and allograft Isograft- a graft of cells, tissue organ from one individual to another individual who is synergic (genetically related) to the donor. allograft- a graft from one individual to a genetically dissimilar individual of the same species. 9. Differentiate between antibodies and TcR (2011,2013) 1) Ig is a four chain antigen binding molecule where as TcR is tow chain antigen binding structure. 2) Ig can undergo somatic mutation to increase diversity but the TcR does not.

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3) Ig can interact with antigen directly, even in solution. In contrast, TcR recognition of antigen occur s obly when antigen is on the surface of a cell, a more precisely when the antigen is bound to cellular particles MHC. 10. Describe the biological function of IL-2 Activation of T and B cell by antigen results in secretion of specific glycoprotein like IL-2. It has profound effects on the proliferation and differentiation of T as well as B cells. 11. What is cytokines(May 2017, 2008, 2013) These are diverse group of small, soluble proteins produced by leukocytes that mediate a variety of immune functions. Those cytokines produced by lymphocytes are some times called lymphokines. Generally, they are secreted by one cell and bind to specific receptors on the corresponding target cell. 12. What is interleukins These are regulatory proteins secreted by monocytes or macrophages or T-lymphocytes. They are involved in signaling between cells of the immune system. 13. Define attenuation? Process of weakening or reducing the virulence of pathogenic organisms without losing the capacity to induce immunity 14. What is boosted dose? A dose of antigen (secondary) given after the primary dose to stimulate accelerated production of large amounts of antibody. 15. List out the attributes that exhibits by cytokines?- Explain it Cytokines exhibit specific attributes to permit cellular activity in a coordinated fashion. It includes • Pleiotropy occurs when a single gene influences multiple phenotypic traits • redundancy is the existence of several genes in the genome of an organism that perform the same role to some extent. • Synergy, in general, may be defined as two or more agents working together to produce a result not obtainable by any of the agents independently. 16. What are the function of TNF? (Jun 2014) The primary role of TNF is in the regulation of immune cells. TNF, being an endogenous pyrogen, is able to induce fever, apoptotic cell death, cachexia, and to inhibit tumorigenesis and viral replication and respond tosepsis via IL1 & IL6 producing cells. Dysregulation of TNF production has been implicated in a variety of human diseases including Alzheimer's disease, cancer, major depression and inflammatory bowel disease (IBD). 17. What are the problem that occur in designing a malaria vaccine Current approaches to design of malaria vaccines focus largely on the sporozoite stage. Nine volunteers were repeatedly immunized by the bite of P. falciparum–infected, irradiated mosquitoes. Later challenge by the bites of mosquitoes infected with virulent P. falciparum revealed that six of the nine recipients were completely protected. These results are encouraging, but translating these findings into mass immunization remains problematic. Sporozoites do not grow well in cultured cells, so an enormous insectory would be required to breed mosquitoes in which to prepare enough irradiated sporozoites to vaccinate just one small village. 18. What is AIDS? (May2016) Acquired immune deficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human virus (HIV). Following initial infection, a person may experience a brief period of influenza-like illness. This is typically followed by a prolonged period without symptoms. As the infection progresses, it interferes more and more with the immune system, making the person much more susceptible to common infections, like tuberculosis, as well as opportunistic infections and tumors that do not usually affect people who have working immune systems. The late symptoms of the infection are referred to as AIDS. 19. Define immunodeficiency disorder? Immunodeficiency disorders prevent your body from adequately fighting infections and diseases. An immunodeficiency disorder also makes it easier for you to catch viruses and bacterial infections in the first place. Doctors often categorize immunodeficiency disorders as either congenital or acquired. A congenital, or primary, disorder is one you were born with. Acquired, or secondary, disorders are disorders you get later in life. Acquired disorders are more common than congenital disorders. 20. What is secondary immune deficiency? (2009) 18 BT6602/Immunology Department of Biotechnology 2018-2019

Immune deficiency may also be the result of particular external processes or diseases; the resultant state is called "secondary" or "acquired" immunodeficiency. Common causes for secondary immunodeficiency are malnutrition, aging and particular medications (e.g. chemotherapy, disease- modifying antirheumatic drugs, immunosuppressive drugs after organ transplants, glucocorticoids). Part B 1. Write a detail account on inflammation 2. Eloborate the immunological response against Mycobacterium tuberculosis (May2017). 3. Explain the various types of cytokines receptor and its function (May 2015, May 2017) 4. Explian the properties and types of cytokines (May 2015) 5. Write a detail account on Alternative pathway of complements (May 2014, 2015) 6. Write a detail account on classical pathway of complements (2008, May 2014, 2015) 7. Explain active and passive vaccination with suitable examples (May 2015) 8. List out the factors to be considered for designing a vaccine and explain the different types of vaccine (May 2015) 9. Explain in detail account the different types of vaccines with suitable examples (2013, May 2016) 10. Write detail account on immune response to bacterial infections 11. Describe in detail about the immune response against viruses and bacteria (2013) 12. Explain protein Vaccines(2011) 13. Explain the mechanism of autoimmune disease with example (May 2016) 1.How the human host reacts against a bacteria and explain the immune mechanisms • Immunity to bacterial infections is achieved by means of antibody unless the bacterium is capable of intracellular growth, in which case delayed-type has an important role. • Bacteria enter the body either through a number of natural routes (e.g., the respiratory tract, the GI tract, and the genitourinary tract) or through normally inaccessible routes opened up by breaks in mucous membranes or skin. Based upon no. of organism host response is exhibited (phagocytosis etc.) • Immune Responses to Extracellular and Intracellular Bacteria Can Differ Extracellular bacteria Infection by extracellular bacteria induces production of humoral antibodies, which are ordinarily secreted by plasma cells in regional lymph nodes and the submucosa of the respiratory and gastrointestinal tracts. • The humoral immune response is the main protective response against extracellular bacteria. • The antibodies act in several ways to protect the host from the invading organisms, including removal of the bacteria and inactivation of bacterial toxins • toxin produced by diphtheria, which exerts a toxic effect on the cell by blocking protein synthesis. • Endotoxins, such as lipopolysaccharides (LPS), are generally components of bacterial cell walls, while exotoxins, such as diphtheria toxin, are secreted by the bacteria. • Antibody-mediated mechanisms for combating infection by extracellular bacteria. 1. Antibody neutralizes bacterial toxins. 2. Complement activation on bacterial surfaces leads to complement-mediated lysis of bacteria. 3. Antibody and the complement split product C3b bind to bacteria, serving as to increase phagocytosis. 4. C3a, C4a, and C5a, generated by antibody initiated complement activation, induce local mast cell degranulation, releasing substances that mediate vasodilation and extravasation of lymphocytes and . 5. Other complement split products are chemotactic for neutrophils and macrophages.

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2.Explain the following i) Hypersensitivity reaction Type I and type III Type I  A type I hypersensitive reaction is induced by certain types of antigens referred to as , and has all the hallmarks of a normal humoral response.  What distinguishes a type I hypersensitive response from a normal humoral response is that the plasma cells secrete IgE.  This class of antibody binds with high affinityto Fc receptors on the surface of tissue mast cells andblood basophils. Mast cells and basophils coated by IgE are  said to be sensitized.  A later exposure to the same cross-links the membrane-bound IgE on sensitized mast cells and basophils, causing degranulation of these cells.  The pharmacologically active mediators released from the granules act on the surrounding tissues.  The principal effects—vasodilation and smooth-muscle contraction—may be either systemic or localized, depending on the extent of mediator release.  ALLERGENS  The majority of humans mount significant IgE responses only as a defense against parasitic infections.  After an individual has been exposed to a parasite, serum IgE levels in increase and remain high until the parasite is successfully cleared from the body.  Some persons, however, may have an abnormality called atopy, a hereditary predisposition to the development of immediate hypersensitivity reactions against common environmental antigens.  The IgE regulatory defects suffered by atopic individuals allow nonparasitic antigens to stimulate inappropriate IgE production, leading to tissuedamaging type I hypersensitivity.  The term allergen refers specifically to nonparasitic antigens capable of stimulating type I hypersensitive responses in allergic individuals  IgE-mediated degranulation begins when an allergen crosslinks IgE that is bound (fixed) to the Fc receptor on the surface of a mast cell or .  The importance of crosslinkage is indicated by the inability of monovalent allergens, which cannot crosslink the fixed IgE, to trigger degranulation. • Allergen crosslinkage of bound IgE results in FcRI aggregation and activation of protein tyrosine kinase (PTK). • PTK then phosphorylates phospholipase C, which converts phosphatidylinositol-4,5 bisphosphate (PIP2) into diacylglycerol • (DAG) and inositol triphosphate (IP3). • DAG activates protein kinase C (PKC), which with Ca2+ is necessary for microtubular assembly and the fusion of the granules with the plasma membrane. IP3 is a potent mobilizer of intracellular Ca2+ stores • 3) Crosslinkage of FcRI also activates an enzyme that converts phosphatidylserine (PS) into phosphatidylethanolamine (PE). • Eventually, PE is methylated to form phosphatidylcholine (PC) by the phospholipid methyl transferase enzymes I and II (PMT I and II). • 4) The accumulation of PC on the exterior surface of the plasma membrane causes an increase in membrane fluidity and facilitates the formation of Ca2+ channels. • the resulting influx of Ca2+ activates phospholipase A2, which promotes the breakdown of PC into lysophosphatidylcholine (lyso PC) and arachidonic acid. • (5) Arachidonic acid is converted into potent mediators: the leukotrienes and prostaglandin D2. • (6) FcRI crosslinkage also activates the membrane adenylate cyclase, leading to a transient increase of cAMP within 15 s. A later drop in cAMP levels is mediated by protein kinase and is 20 BT6602/Immunology Department of Biotechnology 2018-2019

required for degranulation to proceed • (7) cAMP-dependent protein kinases are thought to phosphorylate the granule-membrane proteins, thereby changing the permeability of the granules to water and Ca2+. The consequent swelling of the granules facilitates fusion with the plasma membrane and release of the mediators. The reaction of antibody with antigen generates immune complexes. Generally this complexing of antigen with antibody facilitates the clearance of antigen by phagocytic cells. In some cases, however, large amounts of immune complexes can lead to tissue-damaging type III hypersensitive reactions. When the complexes are formed in the blood, a reaction can develop wherever the complexes are deposited. In particular, complex deposition is frequently observed on blood-vessel walls, in the synovial membrane of joints, on the glomerularbasement membrane of the kidney, on the choroid plexus of the brain. The deposition of these complexes initiates a reaction that results in the recruitment of neutrophils to the site. The tissue there is injured as a consequence of granular release from the neutrophil.

1. Complement initiates mast cell degranulation 2. Neutrophils are chemotactically attracted to the site 3. Neutrophils release lytic enzyme after failed attempts to endocytose the

ii) AIDS and AIDS (Acquired immune deficiency syndrome or acquired immunodeficiency syndrome) is a syndrome caused by a virus called HIV (Human Immunodeficiency Virus). The illness alters the immune system, making people much more vulnerable to infections and diseases. This susceptibility worsens as the syndrome progresses. HIV is found in the body fluids of an infected person (semen and vaginal fluids, blood and breast milk). The virus is passed from one person to another through blood-to-blood and sexual contact. In addition, infected pregnant women can pass HIV to their babies during pregnancy, delivering the baby during childbirth, and through breast feeding. HIV can be transmitted in many ways, such as vaginal, oral sex, anal sex, , and contaminated hypodermic needles. Both the virus and the syndrome are often referred to together

21 BT6602/Immunology Department of Biotechnology 2018-2019 asHIV/AIDS. People with HIV have what is called HIV infection. As a result, some will then develop AIDS. The development of numerous opportunistic infections in an AIDS patient can ultimately lead to death. According to research, the origins of HIV date back to the late nineteenth or early twentieth century in west-central Africa. AIDS and its cause, HIV, were first identified and recognized in the early 1980s. There is currently no cure for HIV or AIDS. Treatments can slow the course of the condition - some infected people can live a long and relatively healthy life.

3.Describe in detail about immunodeficiency diseases with suitable examples • When the system errs by failing to protect the host from disease-causing agents or from malignant cells, the result is immunodeficiency. • Primary Immunodeficiency • Condition resulting from a genetic or developmental defect in the immune system. • Classified based on the part of the immune system affected. • Secondary immunodeficiency or acquired immunodeficiency • The loss of immune function due to exposure to certain agents. Primary Immunodeficiency • A primary immunodeficiency may affect either adaptive or innate immune functions. • Deficiencies involving components of adaptive immunity, such as T or B cells, complements etc. 22 BT6602/Immunology Department of Biotechnology 2018-2019

• The lymphoid cell disorders may affect T cells, B cells, or, in combined immunodeficiencies, both B and T cells. • The myeloid cell disorders affect phagocytic function.

SCID (severe combined immunodeficiency, “bubble boy”) – Several gene defects can cause this disease, most commonly an ADA deficiency – Low numbers of B and T cells – There is a failure to mount immune responses mediated by T cells – Thymus doesn’t develop – Severe recurrent infections, usually fatal in childhood

Fig: David Phillip Vetter (September 21, 1971 – February 22, 1984)

• SCID infants suffer from chronic diarrhea, pneumonia, and skin, mouth, and throat lesions as well as a host of other opportunistic infections. • The immune system is so compromised that even live attenuated vaccines (such as the Sabin polio vaccine) can cause infection and disease. • The life span of SCID patient can be prolonged by preventing contact with all potentially harmful microorganisms. • A defect in the genes that encode mediators of the rearrangement processes (recombination-activating proteins RAG-1 and RAG-2) precludes development of B and T cells with functional receptors and leads to SCID. Bare-lymphocyte syndrome • A defect leading to general failure of immunity similar to SCID is failure to transcribe the genes that encode class II MHC molecules. • Without these molecules, the patient’s lymphocytes cannot participate in cellular interactions with T helper cells.

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X-linked agammaglobulinemia – Defect in light chain rearrangement – Have extremely low IgG and no other classes present. – Individuals with XLA have no peripheral B cells and suffer from recurrent bacterial infections, beginning at about nine months of age. – Rarely survive past teens X-linked hyper-IgM syndrome – Defect in T-cell ability to activate B-cells by T-dependant means (B-cells cannot class switch to IgG, IgA, or IgE). – T-independant activation still occurs – Recurrent infections (especially respiratory) DiGeorge Syndrome – Congenital thymic aplasia in its most severe form is the complete absence of a thymus. – It causes causes immunodeficiency along with characteristic facial abnormalities, hypoparathyroidism, and congenital heart disease – the syndrome is sometimes called the Third and fourth pharyngeal pouch syndrome – Lack of thymus (decreases in both T and B cell activity)

Chronic Granulomatous Disease – Defect in the pathway producing reactive oxygen intermediates (hydrogen peroxide, etc.) – Phagocytes cannot kill phagocytosed bacteria, fungi

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– Gingivitis ("inflammation of the gum tissue”), swollen lymph nodes, subcutaneous granulomas Secondary Immunodeficiency • Immune suppressant drugs (used to combat autoimmune diseases, prevent graft rejection) • Corticosteroid use (, asthma, autoimmune) • HIV/AIDS HIV/AIDS • Contracting HIV – Sexual intercourse – Receipt of infected blood, or blood products – Vertical transmission (mother to fetus) • High risk behaviors – Unprotected sex (multiple partners) – IV drug use – Other active STDs • Nucleocapsid (viral core) – ssRNA – Integrase, reverse transcriptase, and protease enzymes – Protein coat (p17,p24) • Viral envelope (membrane) – gp120 – gp41

• Infection of target cell – HIV gp120 binds to CD4 on target cell – Gp41 and CXCR4 mediates fusion of the viral and T-cell membrane – Nucleocapsid enters the cell, which then releases the RNA and enzymes it contains – Reverse transcriptase transcribes viral RNA into ssDNA – ssDNA is then used to produce dsDNA – dsDNA translocated to nucleus and integrated into chromosome by integrase. (now called the provirus) • Activation of provirus – Transcription factors activate proviral DNA to form mRNA – RNA is exported to cytoplasm – Host-cell ribosomes synthesize viral proteins – Viral protease cleaves viral proteins into active form – ssRNA and viral proteins assemble into new nucleocapsids – Nucleocapsid buds from cell coating itself with membrane containing gp41 and gp120. – New virus is ready to infect another cell.

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4.Outline the working principle and types of vaccines Scientists take many approaches to designing vaccines against a microbe. These choices are typically based on fundamental information about the microbe, such as how it infects cells and how the immune system responds to it, as well as practical considerations, such as regions of the world where the vaccine would be used. The following are some of the options that researchers might pursue:  Live, attenuated vaccines  Inactivated vaccines  Subunit vaccines  Toxoid vaccines  Conjugate vaccines  DNA vaccines  Recombinant vector vaccines LIVE, ATTENUATED VACCINES Live, attenuated vaccines contain a version of the living microbe that has been weakened in the lab so it can’t cause disease. Because a live, attenuated vaccine is the closest thing to a natural infection, these vaccines are good “teachers” of the immune system: They elicit strong cellular and antibody responses and often confer lifelong immunity with only one or two doses. INACTIVATED VACCINES Scientists produce inactivated vaccines by killing the disease-causing microbe with chemicals, heat, or radiation. Such vaccines are more stable and safer than live vaccines: The dead microbes can’t mutate back to their disease-causing state. Inactivated vaccines usually don’t require refrigeration, and they can be easily stored and transported in a freeze-dried form, which makes them accessible to people in developing countries. SUBUNIT VACCINES Instead of the entire microbe, subunit vaccines include only the antigens that best stimulate the immune system. In some cases, these vaccines use epitopes—the very specific parts of the antigen that antibodies or T cells recognize and bind to. Because subunit vaccines contain only the essential antigens and not all the other molecules that make up the microbe, the chances of adverse reactions to the vaccine are lower. TOXOID VACCINES For bacteria that secrete toxins, or harmful chemicals, a toxoid vaccine might be the answer. These vaccines are used when a bacterial toxin is the main cause of illness. Scientists have found that they can inactivate toxins by treating them with formalin, a solution of formaldehyde and sterilized water. Such “detoxified” toxins, called toxoids, are safe for use in vaccines.

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CONJUGATE VACCINES If a bacterium possesses an outer coating of sugar molecules called polysaccharides, as many harmful bacteria do, researchers may try making a conjugate vaccine for it. Polysaccharide coatings disguise a bacterium’s antigens so that the immature immune systems of infants and younger children can’t recognize or respond to them. Conjugate vaccines, a special type of subunit vaccine, get around this problem. DNA VACCINES Once the genes from a microbe have been analyzed, scientists could attempt to create a DNA vaccine against it. Genes for a microbe’s antigens are introduced into the body, some cells will take up that DNA. The DNA, then instructs those cells to make the antigen molecules. The cells secrete the antigens and display them on their surfaces. In other words, the body’s own cells become vaccine-making factories, creating the antigens necessary to stimulate the immune system. RECOMBINANT VECTOR VACCINES Recombinant vector vaccines are experimental vaccines similar to DNA vaccines, but they use an attenuated virus or bacterium to introduce microbial DNA to cells of the body. “Vector” refers to the virus or bacterium used as the carrier. In nature, viruses latch onto cells and inject their genetic material into them. In the lab, scientists have taken advantage of this process. They have figured out how to take the roomy genomes of certain harmless or attenuated viruses and insert portions of the genetic material from other microbes into them. The carrier viruses then ferry that microbial DNA to cells. Recombinant vector vaccines closely mimic a natural infection and therefore do a good job of stimulating the immune system.

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UNIT-IV TRANSPLANTATION AND TUMOR IMMUNOLOGY 1. Define transplantation Transplantation refers to the implantation of tissue from on individual to another. The implanted tissue is called graft or transplant. 2. What is autograft It refers to a graft that take place within the same individual. It is a tissue of an individual is removed from one place and is implanted in another place of the same individual. 3. What is syngraft It is grafts that takes place between tow genetically identical individual of the same species. It is a graft between identical twins or between inbred strains of the same species. Formerly syngraft was called isograft 4. Define allograft (2008, May 2017) It is the transfer of tissues between two genetically distinct members of the same species. The allograft was formerly named as homograft. 5. What is xenograft (2011, Nov2013) It is graft or transfer of tissues between two individuals of two different species. Formerly xenograft was named as heterograft. 6. What is graft acceptance When transplantation is made between genetically identical individuals the graft survives and lives as healthy as it is in the original place. When the graft tissue remains alive it is said to be accepted and the process is called graft acceptance. 7. Define graft rejection (Dec 2013) When transplantation is made between genetically distinct individuals, the graft tissue dies and decays. When the graft tissue dies, the graft is said to be rejected and the process is called graft rejection. 8. Explain the host-versus graft reaction In most transplantation experiments, the graft tissue antigens induce an immune response in the host. This type of immune response is called host versus graft reaction. 9. What is Graft versus host reaction It is the reaction in which the gaft tissue elicites an immune response against the host antigens. 10. What is meant by immunosuppression? (2008, 2013, 2015) Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other conditions. Deliberately induced immunosuppression is generally done to prevent the body from rejecting an organ transplant, treating graft-versus-host disease after a bone marrow transplant, or for the treatment of auto- immune diseases such as rheumatoid arthritis or Crohn's disease. This is typically done using drugs, but may involve surgery (splenectomy), plasmapharesis, or radiation. 11. List the immunosuppressive drugs The common drugs used for immunosuppression include azothoprine, methotrexate, cyclophosphamide, cyclosporine, steroids. Etc. 12. What is acute rejection It is a quick graft rejection. It is further classified into two sub types namely early acute rejection and late acute rejection. 13. What is hyper acute rejection It is a very quick rejection. It is similar to second set rejection. It is due to pre-existing humoral antibodies in the serum of the host as a result of presensitization with previous grafts, pregnancies and blood transfusion. 14. What is insidious rejection It is a secret rejection due to deposition of immune complexes on tissues like glomerular membrane that can be demonstrated in kidney by immunofluorecence. 15. What is first set rejection When graft is made between genetically different individuals, the graft gets blood supply from the host and it appears to be normal for the first 3 days. But on the 5th day, sensitized T-cells, macrophages and a few plasma cells invade the graft and the graft is rejected. This is called first set rejection. 28 BT6602/Immunology Department of Biotechnology 2018-2019

16. What is immunological enhancement Certain antibodies may not cause allograft rejection. Instead, they facilitate the growth of allografts. The facilitating effect of antibodies on the growth of allograft is called immunological enhancement. The antibodies helping in the growth of allograft are called enhancing or blocking antibodies. 17. Define Tumour It is an independent, autonomous, uncontrolled growth of tissue containing a mass of abnormal cells. They are classified into tow types- Malignant tumour and Benign tumour. 18. What are tumor antigens? (2008) Two types of tumor antigens have been identified on tumor cells: tumor-specific transplantation antigens (TSTAs) and tumor-associated transplantation antigens (TATAs). Tumor-specific antigens are unique to tumor cells and do not occur on normal cells in the body. They may result from mutations in tumor cells that generate altered cellular proteins; cytosolic processing of these proteins would give rise to novel peptides that are presented with class I MHC molecules, inducing a cell-mediated response by tumor- specific CTLs (Figure 22-6). Tumor-associated antigens, which are not unique to tumor cells, may be proteins that are expressed on normal cells during fetal development when the immune system is immature and unable to respond but that normally are not expressed in the adult. Reactivation of the embryonic genes that encode these proteins in tumor cells results in their expression on the fully differentiated tumor cells. Tumor-associated antigens may also be proteins that are normally expressed at extremely low levels on normal cells but are expressed at much higher levels on tumor cells. 19. What is Malignant tumour Malignant tumours are tumours which grow rapidly and spread from one place to another. 20. What is Banign tumour Banign tumours are tumours which grow slowly and it does not spread from one place to another. 21. What is Carcinoma The tumour arising from epithelial cells is called carcinoma 22. What is Sarcoma The tumour arising from the mesenchymal tissues, connective tissues and endothelial cells, is called sarcoma 23. What is Lymphoma The tumour arising from lymphoid tissue is called lymphoma 24. What is a granuloma? (2009) Granuloma is a medical term for a ball-like collection of immune cells which forms when the immune system attempts to wall off substances that it perceives as foreign but is unable to eliminate. Such substances include infectious organisms such as bacteria and fungi as well as other materials such as keratin, suture fragments and vegetable particles. A granuloma is therefore a special type of inflammatory reaction that can occur in a wide variety of diseases, both infectious and non-infectious 25. Define Immune surveillance The careful watching, identification and killing of the tumour cells by the immune system is called immune surveillance or immunological surveillance. 26. What is Null cells Null cells are lymphocytes with cytotoxic properties. They are intermediate between T and B cells. They are two types- Natural killer cells and killer cells 27. What is the role of T Helper cells in the immune response T helper cells are a sub population of T lymphocytes that help B cells and other T cells in immune responses. They are the regulator cells, which are activated even by very small quantities of antigens which cannot activate other cells. 28. What is the role of T suppressor cells in immune response T suppressor cells are a sub population of T lymphocytes that suppress the activity of B cells and other T cells. They are the regulator cells, which inhibit antibody production by B cells. They suppress the functions of the T killer cells and T helper cells. 2. Write a short note on HLA typing (May2016) HLA typing is usually done by a special blood test that checks the antigens. Antigens on the donated stem cells need to be exactly the same as, or very similar to, those on the recipient’s cells. At least 6–10 specific antigens need to match. A perfect match is 6 out of 6 (6/6) or 10/10, but a transplant may be done if there 29 BT6602/Immunology Department of Biotechnology 2018-2019

is a less than perfect match (5/6 or 9/10). The highest likelihood of finding a perfect match is within the recipient’s own family (usually a brother or sister). 29. What are DNA vaccine (May 2017) DNA vaccination is a technique for protecting against disease by injection with genetically engineered DNA so cells directly produce an antigen, producing a protective immunological response. DNA vaccines have potential advantages over conventional vaccines, including the ability to induce a wider range of immune response types. Several DNA vaccines are available for veterinary use. Currently no DNA vaccines have been approved for human use. Research is investigating the approach for viral, bacterial and parasitic diseases in humans, as well as for several cancers 30. What is the role of T cytotoxic cells T cytotoxic cells are a sub population of T lymphocytes that can directly attack a cell, thereby capable of killing microorganisms and at times even some of the body’s own cells. Part B 1. Explain how Graft donors and recipients are typed for RBC and MHC antigens 2. Write a detail account on Transplantation (2011, Nov 2013) 3. Explain the different types of transplant and their significances in transplantation immunology (2013) 4. Write a detail account on Tumors and its diagnosis (2012, May 2016) 5. Explain the mechanism of immunity to tumor antigen (2008) 6. Explain the mechanism of allograft rejection. Describe the methods available to prevent allograft rejection (2008, May 2016). 7. Narrate the steps involved in the graft rejection reaction (May 2017). 8. What are tumor antigens and explain how tumor cells evade from the immune recognition and activation (May 2017). 9. Discuss the various factors that need to be considered for an organ transplant and the immunological mechanisms behind it (2007). 10. Describe in detail the role of viruses in cancer development with suitable examples (Nov2013)

1.Describe in detail the role of viruses in cancer development with suitable examples Several viruses are linked with cancer in humans. Our growing knowledge of the role of viruses as a cause of cancer has led to the development of vaccines to help prevent certain human cancers. But these vaccines can only protect against infections if they are given before the person is exposed to the cancer-promoting virus. Human papilloma viruses (HPVs) Human papilloma viruses (HPVs) are a group of more than 150 related viruses. They are called papilloma viruses because some of them cause papillomas, which are more commonly known as warts. Some types of HPV only grow in skin, while others grow in mucous membranes such as the mouth, throat, or vagina. All types of HPV are spread by contact (touch). More than 40 types of HPV can be passed on through sexual contact. Most sexually active people are infected with one or more of these HPV types at some point in their lives. At least a dozen of these types are known to cause cancer. While HPV infections are very common, cancer caused by HPV is not. Most people infected with HPV will not develop a cancer related to the infection. HPV infections of the mucous membranes can cause genital warts, but they usually have no symptoms. There are no effective medicines or other treatments for HPV, other than removing or destroying cells that are known to be infected. But in most people, the body’s immune system controls the HPV infection or gets rid of it over time. HPV and cervical cancer A few types of HPV are the main causes of cervical cancer, which is the second most common cancer among women worldwide. Cervical cancer has become much less common in the United States because the Pap test has been widely available for many years. This test can show pre- cancerous changes in cells of the cervix that might be caused by HPV infection. These changed 30 BT6602/Immunology Department of Biotechnology 2018-2019 cells can then be destroyed or removed, if needed. This can keep cancer from developing. Doctors may now also test for HPV, which can tell them if a woman might be at higher risk for cervical cancer. Nearly all women with cervical cancer show signs of HPV infection on lab tests, but most women infected with HPV will not develop cervical cancer. Even though doctors can test women for HPV, there is no treatment directed at HPV itself. If the HPV causes abnormal cells to start growing, these cells can be removed or destroyed. HPV and other cancers HPVs also have a role in causing some cancers of the penis, anus, vagina, and vulva. They are linked to some cancers of the mouth and throat, too. Again, although HPVs have been linked to these cancers, most people infected with HPV never develop these cancers. Smoking, which is also linked with these cancers, may work with HPV to increase cancer risk. Other genital infections may also increase the risk that HPV will cause cancer. You can get more details in HPV and Cancer. Vaccines against HPV Vaccines are now available to help protect against infection from the main cancer-causing HPV types. These vaccines are approved for use in females from age 9 up to their mid-20’s. Some HPV vaccines have also been approved for use in boys and young men. The vaccines can only be used to help prevent HPV infection – they do not stop or help treat an existing infection. To be most effective, the vaccines should be given before a person becomes sexually active (has sex with another person). Because the vaccines are still fairly new (first approved in 2006), and it often takes decades for cancer to develop, it’s not yet known how well they will protect against it, or exactly which types of cancers they might help prevent. These vaccines and others like them are being studied further. Epstein-Barr virus (EBV) EBV is a type of herpes virus. It is probably best known for causing infectious mononucleosis, EBV can be passed from person to person by coughing, sneezing, or by sharing drinking or eating utensils. Most people in the United States are infected with EBV by the end of their teen years, although not everyone develops the symptoms of mono. As with other herpes virus infections, EBV infection is life-long, even though most people have no symptoms after the first few weeks. EBV infects and stays in certain white blood cells in the body called B lymphocytes (also called Bcells). There are no medicines or other treatments to get rid of EBV, nor are there vaccines to help prevent it, but EBV infection doesn’t cause serious problems in most people. EBV infection increases a person’s risk of getting nasopharyngeal cancer (cancer of the area in the back of the nose) and certain types of fast-growing lymphomas such as Burkitt lymphoma. It may also be linked to Hodgkin lymphomaand some cases of stomach cancer. EBV-related cancers are more common in Africa and parts of Southeast Asia. Overall, very few people who have been infected with EBV will ever develop these cancers. Hepatitis B virus (HBV) and hepatitis C virus (HCV) Both HBV and HCV cause viral hepatitis, a type of liver infection. Other viruses can also cause hepatitis (hepatitis A virus, for example), but only HBV and HCV can cause the long-term (chronic) infections that increase a person’s chance of liver cancer. In the United States, less than half of liver cancers are linked to HBV or HCV infection. But this number is much higher in some other countries, where both viral hepatitis and liver cancer are much more common. Some research also suggests that long-term HCV infection might be linked with some other cancers, such as non- Hodgkin lymphoma. HBV and HCV are spread from person to person in much the same way as HIV (see the section on HIV below) — through sharing needles (such as during injection drug use), unprotected sex, or

31 BT6602/Immunology Department of Biotechnology 2018-2019 childbirth. They can also be passed on through blood transfusions, but this is rare in the United States because donated blood is tested for these viruses. Of the 2 viruses, infection with HBV is more likely to cause symptoms, such as a flu-like illness and jaundice (yellowing of the eyes and skin). Most adults recover completely from HBV infection within a few months. Only a very small portion of adults go on to have chronic HBV infections, but this risk is higher in young children. People with chronic HBV infections have a higher risk for liver cancer.

2.Explain the different types of grafts for transplantation of organs and their significance Types of Transplants: • Autograft – Self tissue transferred from one site to another • Isograft – Genetically identical individuals • Allograft – Different members of the same species • Xenograft – Different species Prevention of allograft rejection • Histocompatable tissues – tissues that are antigenically similar. • There are more than 40 genes that determine histocompatability, but the most imporant are the MHC (HLA) genes. • Graft donors are typed for RBC and MHC antigens. Clinical Manifestations of Graft rejection • Hyperacute rejection (rare) – Occurs immediately – Due to pre-formed antibodies • Patients had previous blood transfusions • Patient had multiple pregnancies • Previous graft • Acute rejection – Occurs in about 10 days – Activated T cells, NK cells, macrophages, ADCC, complement mediate damage • Chronic rejection – Months to years later – Immunosuppressent drugs prevent acute graft rejection, but not chronic rejection – Thought to be due to low grade cell-mediated responses that gradually scar the vasculature of the graft, leading to arteriosclerosis. Allograft Rejection Displays Specificity and Memory • The rate of allograft rejection varies according to the tissue involved. • In general, skin grafts are rejected faster than other tissues such as kidney or heart.

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3. Discuss the mechanism of tumor and its diagnosis.  Tumour is an independent autonomous, uncontrolled growth of a tissue containing a mass of abnormal cells.  Based on the spreading tumours are classified into two types, namely malignant tumour and non malignant tumours Malignant tumours are tumours which grow rapidly and spread from one place to another.  Benign tumour-Benign tumours are tumours which grow slowly and it does not spread from one place to another.  Carcinoma-The tumour arising from epithelial cells is called carcinoma Sarcoma-The tumour arising from the mesenchymal tissues, connective tissues and endothelial cells, is called sarcoma-Lymphoma  The tumour arising from lymphoid tissue is called lymphoma-Leukemia-The tumor of the white blood cells is called leukemia  Immune response to tumour- tumor cells are completely altered from normal cells and they have new set of antigens. Hence a tumour behaves as an allograft.  The immune system recognizes it as non self and an immune response is elicited to kill or remove the tumour.  The immune system responds in the following methods- generation tumour specific cytotoxic T cells- generation of T- helper cells- production tumour specific cytotoxic antibodies- stimulation of NK cells- production lymphokines activated killer cells.

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UNIT-V ALLERGY,HYPERSENSITIVITY AND 1. Define Hypersensitivity It is defined as the violent reaction of the mmune system leading to severe symptoms and even death in a sensitized animal when it is reexposed to the same antigen for the second time. 2. What is contact hypersensitivity reaction? (2009) It is defined as the violent reaction of the Immune system leading to severe symptoms and even death in a sensitized animal when it is reexposed to the same antigen for the second time. 3. What is delayed hypersensitivity A tissue damaging immunological reaction mediated by T lymphocytes and the visible manifestation of the reaction occur in a delayed state after 48 hours. 4. Define anaphylaxis It defined as exaggerated reactions of an organism to a foreign substance to which it has previously become sensitized resulting from the release of histamine, serotonin and other vasoactive substances. 5. What is Type II hypersensitivity It is due to the interactions of antibodies and cell associated antigens. When antibodies attach to the antigens located on the surface of cells the cells become cytotoxic. Hence type II hypersensitivity is also called antibody dependent cytotoxic hypersensitivity. 6. What is meant by immunotherapy? (2007) Immunotherapy is a medical term defined as "treatment of disease by inducing, enhancing, or suppressing an immune response. Immunotherapies designed to elicit or amplify an immune response are classified as activation immunotherapies. Immunotherapies designed to reduce, suppress or more appropriately direct an existing immune response, 7. Give any two examples of auto immune diseases. (2008) Thyroiditis and Goodpasture’s disease 8. What is localized autoimmune disease In localized autoimmune disease, a particular organ is affected due to . Hence it is also called organ specific autoimmune disease 9. What is systemic autoimmune disease (2011) It is a autoimmune disease in which it affects the whole body or many organs. Hence it is called non- organ specific autoimmune diseases. 10. What is autoimmune Haemolytic anaemia It is a clinical disorder where there is a reduction below normal of the numbr of RBCs or quantity of haemoglobin. The reduction in RBC number is caused by the destruction or lysis of RBCs. This is due to the production of untoanntibodies against antigens present on the RBCs. 11. What is thrombocytopenia It is an autoimmune disease characterized by low count. It is due to the production of antiplatelet antibodies of the type Ig G. 12. What is Addison’s disease? (Nov2013) It is due to adrenocortical damage and hence insufficient secretion of adrenocortical hormones. The tissue damage is caused by auto antibodies against zona glomerulosa cells of adrenal cortex 13. Define Myasthenia Gravis It is disease of skeletal muscle characterized by gradually increasing weakness of muscles that make one easily fatigue. This disease is caused by against muscle antigen and acetylcholine receptor antigen. 14. What are the symptoms of Rheumatoid arthritis? (Nov 2013) It is a chronic systemic disease of the joints marked by inflammatory changes in the synovial membrane and atricular structures and by atrophy of bones. This disease is caused by autoantibodies of the type IgM. The synovial fluids of these patients contain increased number of T cells and macrophages. 15. What is isoimmune reactions The reaction brought about by the antigen and antibodies of two individuals belonging to the same species are isoimmune reactions. 16. What is Transfusion reaction The agglutination or lysis of recipient blood due to mismatched blood groups is called transfusion reaction. It occurs in ABO blood groups as as Rh blood group. 34 BT6602/Immunology Department of Biotechnology 2018-2019

17. What is erythroblastosis foetalis (2015, May 2017) It is a haemolytic disease caused by the reaction of Rh antigen and Rh antibody. It occurs in the Rh+ baby developing in an Rh- mother. The Rh antibody involved in this reaction belongs to Ig G type. 18. Define Autoimmunity Autoimmunity in the reaction bought about by the interaction of antigen and antibody of the same individual is called autoimmune reaction. 19. What is Arthus reaction It is a local immune complex reaction produced on the skin by the intradermal injection of non toxic foreign substances like horse serum egg albumin, etc. into rabbits or guinea pigs. These reaction may cause erythema, induration, odema, haemorrhage and necrosis. 20. What is It is an immune complex disease caused by the enormous amount of foreign serum, such as antidiphtheria antiserum, antitetanus antiserum. 21. What is Mantoux reaction It is type IV hypersensitivity. It is due to the interaction of sensitized T cells and tuberculin bacterium. When a small dose of tuberculin is injected intradermally in an individual already sensitized to tuberculo protein by prior infection, the reaction occurs. In unsensitized animals, the tuberculin injection provokes no response. The Mantoux reaction therefore indicated tuberculin infection in children. 22. What is the role of rheumatoid factors? Rheumatoid factor (RF) is the autoantibody (antibody directed against an organism's own tissues) that was first found in rheumatoid arthritis. It is defined as an antibody against the Fc portion of IgG (an antibody against an antibody). RF and IgG join to form immune complexes that contribute to the disease process. Rheumatoid factor can also be a cryoglobulin; it can be either type 2 or type 3 (polyclonal IgM to polyclonal IgG) cryoglobulin. Although predominantly encountered as IgM, Rheumatoid factor can be of any of immunoglobulins, i.e. IgA, IgG, IgM,IgE,IgD. 23. What is alloimmunity (May 2014) Alloimmunity is an immune response to foreign antigens (alloantigens) from members of the same species. The body attacks especially transplanted tissue and even the fetus in some cases. Alloimmune response results in graft rejection, which is manifested as deterioration or complete loss of graft function. In contrast, autoimmunity is an immune response to the self's own proteins. Alloimmunity is caused by the difference between products of highly polymorphic genes, primarily genes of MHC complex, of the donor and graft recipient. These products are recognized by T-lymphocytes and other mononuclear leukocytes which infiltrate the graft and damage it.

24. Outline the principle and application of RIA (May 2016) Radioimmunoassay (RIA) is a very sensitive in vitro assay technique used to measure concentrations of antigens (for example, hormone levels in blood) by use of antibodies. As such, it can be seen as the inverse of a radiobinding assay, which quantifies an antibody by use of corresponding antigens. Although the RIA technique is extremely sensitive and extremely specific, requiring specialized equipment, it remains among the least expensive methods to perform such measurements. It requires special precautions and licensing, since radioactive substances are used. The RAST test (radioallergosorbent test) is an example of radioimmunoassay. It is used to detect the causative allergen for an allergy. 25. Define SCID (May 2016) Severe combined immunodeficiency (SCID) also known as alymphocytosis, Glanzmann–Riniker syndrome, severe mixed immunodeficiency syndrome, and thymic alymphoplasia, is an extremely rare genetic disorder characterized by the disturbed development of functional T cells and B cells caused by numerous genetic mutations that result in heterogeneous clinical presentations. SCID involves defective antibody response due to either direct involvement with B lymphocytes or through improper B lymphocyte activation due to non-functional T-helper cells. 26. Define systemic lupus erythematosus(May 2017) Systemic lupus erythematosus (SLE), also known simply as lupus, is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary between people and may be mild to severe. Common symptoms include painful and swollen

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joints, fever, chest pain, hair loss, mouth ulcers, swollen lymph nodes, feeling tired, and a red rash which is most commonly on the face. 27. What is Thyrotoxicosis or Grave’s disease It is a disease condition owing to the overactivity of thyroid gland. It is caused by an antibody called long acting thyroid stimulator (LATS). It is an Ig G type. It acts on the thyroid cell surface antigen which is basically receptor for thyroid stimulating hormone produced by the pituitary gland. This causes the release of thyroxine in higher dose from the thyroid cells. This causes the Grave’s disease Part B 1. Discuss the immunological responses involved in the pathogensis of an autoimmune disorder (May 2017) 2. Explain the mechanism of autoimmune disease with examples (May 2016) 3. Write in detail about anaphylaxis and cell mediated hypersensitive (May 2016) 4. Write a detail account on autoimmunity? (2008, 2009, 2015) 5. Explain the different types of autoimmune disorders and their diagnostics methods (2011, 2013, 2014) 6. What is auto immunity? Explain the auto immunity with two examples (2008, 2009) 7. Write detail account on immune response to viral infections (2013) 8. Write detail account on immune response to parasite infections 9. Explain in detail about immunosuprresion and immunesuppresive drug 10. Write a detail account on recombinant vaccines 11. Give a detail account on tumour immunology (2013) 12. Write a detail account on AIDS(Nov 2013) 13. Explain the various therapies for curing autoimmune diseases (May 2014) 14. Write a detail account on Hypersensitive Type I with suitable example (2008, 2009) 15. What is an allergic reaction? Explain Type I and Type III hypersensitivity reactions(May 2017). 16. Explain the immune complex mediated hypersensitivity.

1.What is autoimmunity? Explain the proposed mechanism for induction of autoimmunity Early in the last century , Paul Ehrlich realized that the immune system could go awry and, instead of reacting against foreign antigens, could focus its attack on self-antigens. He termed this condition “horror autotoxicus.” In the 1960s, it was believed that all self-reactive lymphocytes were eliminated during their development in the bone marrow and thymus and that a failure to eliminate these lymphocytes led to autoimmune consequences. • Since the late 1970s, a broad body of experimental evidence has countered that belief, revealing that not all self-reactive lymphocytes are deleted during T-cell and B-cell maturation. • Instead, normal healthy individuals have been shown to possess mature, recirculating, self- reactive lymphocytes. • Since the presence of these self-reactive lymphocytes in the periphery does not inevitably result in autoimmune reactions, their activity must be regulated in normal individuals through or clonal suppression. • Factors that predispose individuals to autoimmunity • HLA (MHC) alleles – such as HLA-B27 • TH1 vs. TH2 balance - > TH1 responses implicated in increased autoimmunity • Mechanism of Induction • Release of sequestered antigen • Molecular mimicry Inappropriate MHC II expression

2. Explain the different types of autoimmune disorder and their diagnostics methods Hashimoto’s thyroiditis: • It is most frequently seen in middle-aged women, an individual produces auto-antibodies

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and sensitized TH1 cells specific for thyroid antigens. • DTH (type for hypersensitivty) is characterized by an intense infiltration of the thyroid gland by lymphocytes, macrophages, and plasma cells, which form lymphocytic follicles and germinal centers to self antigens • Antibodies are formed to a number of thyroid proteins, including thyroglobulin and thyroid peroxidase, both of which are involved in the uptake of iodine. Result – hypothyroidism, goiter • Which leads to decreased production of thyroid hormones Goodpasture’s Syndrome – Type II hypersensitivity to self antigens – Autoantigen – basement membranes of kidney and alveoli of lungs – Subsequent complement activation leads to direct cellular damage and an ensuing inflammatory response mediated by a buildup of complement split products. – Result – progressive kidney damage and pulmonary hemorrhage. Insulin-Dependent diabetes mellitus – DTH response (Type IV) to self antigens – is caused by an autoimmune attack on the pancreas. – Autoantigen – beta cells of the islets of Langerhans (pancreas) – The autoimmune attack destroys beta cells, resulting in decreased production of insulin and consequently increased levels of blood glucose. – Several factors are important in the destruction of beta cells. – First, activated CTLs migrate into an islet and begin to attack the insulin producing cells. – Local production during this response includes IFN-, TNF-, and IL-1. – Auto-antibody production can also be a contributing factor in IDDM. – Result – inability to produce and secrete insulin Grave’s Disease-Type II hypersenstivity to self antigens • The production of thyroid hormones is carefully regulated by thyroid-stimulating hormone (TSH), which is produced by the pituitary gland. • Binding of TSH to a receptor on thyroid cells activates adenylate cyclase and stimulates the synthesis of two thyroid hormones, thyroxine and triiodothyronine. • A patient with Graves’ disease produces auto-antibodies that bind the receptor for TSH and mimic the normal action of TSH, activating adenylate cyclase and resulting in production of the thyroid hormones. – unregulated stimulation of TSH receptor leading to hyperthyroidism Myasthenia Gravis- Type II hypersensitivity to self antigens • A patient with this disease produces auto-antibodies that bind the acetylcholine receptors on the motor end-plates of muscles, blocking the normal binding of acetylcholine and also inducing complement mediated lysis of the cells. • The result is a progressive weakening of the skeletal muscles. • Ultimately, the antibodies destroy the cells bearing the receptors. • The early signs of this disease include drooping eyelids and inability to retract the corners of the mouth, which gives the appearance of snarling. – Autoantigen – ACh receptor – Result – blockage and damage to ACh receptor with destruction of endplate leading to muscle weakness Systemic Lupus Erythematosus-Type III (immune complex disease) – Autoantigens – DNA, histones, RBCs, , leukocytes, clotting factors. – SLE which typically appears in women between 20 and 40 years of age; the ratio of female to male patients is 10:1. SLE 37 BT6602/Immunology Department of Biotechnology 2018-2019

– Auto-antibody specific for RBCs and platelets, for example, can lead to complement-mediated lysis, resulting in hemolytic anemia and thrombocytopenia, respectively – When immune complexes of auto-antibodies with various nuclear antigens are deposited along the walls of small blood vessels, a type III hypersensitive reaction develops. – that damage the wall of the blood vessel, resulting in vasculitis and glomerulonephritis. – Results- fever, rashes, weakness, arthritis, pleurisy, kidney dysfunction

3.Write in detail about anaphylaxis and cell mediated hypersensitivity. IgE-Mediated (Type I) Hypersensitivity A type I hypersensitive reaction is induced by certain types of antigens referred to as allergens, and has all the hallmarks of a normal humoral response. What distinguishes a type I hypersensitive response from a normal humoral response is that the plasma cells secrete IgE. This class of antibody binds with high affinity to Fc receptors on the surface of tissue mast cells andblood basophils. Mast cells and basophils coated by IgE are said to be sensitized. A later exposure to the same allergen cross-links the membrane-bound IgE on sensitized mast cells and basophils, causing degranulation of these cells. The pharmacologically active mediators released from the granules act on the surrounding tissues. The principal effects—vasodilation and smooth-muscle contraction—may be either systemic or localized, depending on the extent of mediator release. There Are Several Components of Type I Reactions ALLERGENS The majority of humans mount significant IgE responses only as a defence against parasitic infections. After an individual has been exposed to a parasite, serum IgE levels in increase and remain high until the parasite is successfully cleared from the body. • Some persons, however, may have an abnormality called atopy, a hereditary predisposition to the development of immediate hypersensitivity reactions against common environmental antigens. • The IgE regulatory defects suffered by atopic individuals allow nonparasitic antigens to stimulate inappropriate IgE production, leading to tissue damaging type I hypersensitivity. • The term allergen refers specifically to nonparasitic antigens capable of stimulating type I hypersensitive responses in allergic individuals

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• Ig E Cross linkage Initiates Degranulation- Ig E -mediated degranulation begins when an allergen crosslinks IgE that is bound (fixed) to the Fc receptor on the surface of a mast cell or basophil. • The importance of crosslinkage is indicated by the inability of monovalent allergens, which cannot crosslink the fixed IgE, to trigger degranulation. • Allergen crosslinkage of bound IgE results in FcRI aggregation and activation of protein tyrosine kinase (PTK). • (1) PTK then phosphorylates phospholipase C, which converts phosphatidylinositol-4,5 bisphosphate (PIP2) into diacylglycerol (DAG) and inositol triphosphate (IP3). • (2) DAG activates protein kinase C (PKC), which with Ca2+ is necessary for microtubular assembly and the fusion of the granules with the plasma membrane. IP3 is a potent mobilizer of intracellular Ca2+ stores. • 3) Crosslinkage of FcRI also activates an enzyme that converts phosphatidylserine (PS) into phosphatidylethanolamine (PE). • Eventually, PE is methylated to form phosphatidylcholine (PC) by the phospholipid methyl transferase enzymes I and II (PMT I and II). • 4) The accumulation of PC on the exterior surface of the plasma membrane causes an increase in membrane fluidity and facilitates the formation of Ca2+ channels. • the resulting influx of Ca2+ activates phospholipase A2, which promotes the breakdown of PC into lysophosphatidylcholine (lyso PC) and arachidonic acid. • (5) Arachidonic acid is converted into potent mediators: the leukotrienes and prostaglandin D2. • (6) FcRI crosslinkage also activates the membrane adenylate cyclase, leading to a transient increase of cAMP within 15 s. A later drop in cAMP levels is mediated by protein kinase and is required for degranulation to proceed. • 7) cAMP-dependent protein kinases are thought to phosphorylate the granule-membrane proteins, thereby changing the permeability of the granules to water and Ca2+. The consequent swelling of the granules facilitates fusion with the plasma membrane and release of the mediators. Type I Hypersensitivity:Systemic or Localized • Systemic (Anaphylaxis shock) – Symptoms include: labored breathing, drop in blood pressure, smooth muscle contraction, bronchiole constriction (suffocation) • Localized – Examples: Hay fever (allergic rhinitis), asthma (allergic or intrinsic), food allergies, atopic dermatitis (eczema) Cell Mediated Hypersensitivity When some subpopulations of activated TH cells encounter certain types of antigens, they secrete cytokines that induce a localized inflammatory reaction called delayed-type hypersensitivity (DTH). The reaction is characterized by large influxes of nonspecific inflammatory cells, in particular, macrophages. (tuberculin test) The hallmarks of a type IV reaction are the delay in time required for the reaction to develop and the recruitment of macrophages as opposed to neutrophils, as found in a type III reaction • Sensitization phase: The development of the DTH response begins with an initial sensitization phase of 1–2 weeks after primary contact with an antigen. • During this period, TH cells are activated and clonally expanded by antigen presented together with the requisite class II MHC molecule on an appropriate antigen presenting cell. • A variety of antigen-presenting cells have been shown to be involved in the activation of a DTH response, including Langerhans cells and macrophages.

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Effector Phase • A subsequent exposure to the antigen induces the effector phase of the DTH response. • In the effector phase, TH1 cells secrete a variety of cytokines that recruit and activate macrophages and other nonspecific inflammatory cells. • A DTH response normally does not become apparent until an average of 24 h after the second contact with the antigen; the response generally peaks 48–72 h after second contact. • The delayed onset of this response reflects the time required for the cytokines to induce localized influxes of macrophages and their activation. • Once a DTH response begins, a complex interplay of nonspecific cells and mediators is set in motion that can result in tremendous amplification. • By the time the DTH response is fully developed, only about 5% of the participating cells are antigen-specific TH1 cells; the remainder are macrophages and other nonspecific cells.

4.Explain the mechanism of autoimmune disease with examples In an organ-specific autoimmune disease, the immune response is directed to a target antigen unique to a single organ or gland, so that the manifestations are largely limited to that organ. The cells of the target organs may be damaged directly by humoral or cell-mediated effector mechanisms. Alternatively, the antibodies may overstimulate or block the normal function of the target organ. Systemic Autoimmune Diseases In systemic autoimmune diseases, the response is directed toward a broad range of target antigens and involves a number of organs and tissues. These diseases reflect a general defect in immune regulation that results in hyperactive T cells and B cells. Tissue damage is widespread, both from cellmediated immune responses and from direct cellular damage caused by auto-antibodies or by accumulation of immune complexes. Autoimmune diseases Autoimmune diseases involving direct cellular damage occur when lymphocytes or antibodies bind to cell-membrane antigens, causing cellular lysis and/or an inflammatory response in the affected organ. Gradually, the damaged cellular structure is replaced by connective tissue (scar tissue), and the function of the organ declines. This section briefly describes a few examples of this type of autoimmune disease. Hashimoto’s Thyroiditis In Hashimoto’s thyroiditis, which is most frequently seen in middle-aged women, an individual produces auto-antibodies and sensitized TH1 cells specific for thyroid antigens. The DTH response is characterized by an intense infiltration of the thyroid gland by lymphocytes, macrophages, and plasma cells, which form lymphocytic follicles and germinal centers The ensuing inflammatory response causes a goiter, or visible enlargement of the thyroid gland, a physiological response to hypothyroidism. Antibodies are formed to a number of thyroid proteins, including thyroglobulin and thyroid peroxidase, both of which are involved in the uptake of iodine. Binding of the auto-

40 BT6602/Immunology Department of Biotechnology 2018-2019 antibodies to these proteins interferes with iodine uptake and leads to decreased production of thyroid hormones (hypothyroidism). Autoimmune anemias include pernicious anemia, autoimmune hemolytic anemia, and drug- induced hemolytic anemia. Pernicious anemia is caused by auto-antibodies to intrinsic factor, a membrane-bound intestinal protein on gastric parietal cells. Intrinsic factor facilitates uptake of vitamin B12 from the small intestine. Binding of the auto-antibody to intrinsic factor blocks the intrinsic factor–mediated absorption of vitamin B12. In the absence of sufficient vitamin B12, which is necessary for proper hematopoiesis, the number of functional mature red blood cells decreases below normal. Pernicious anemia is treated with injections of vitamin B12, thus circumventing the defect in its absorption. An individual with autoimmune hemolytic anemia makes auto-antibody to RBC antigens, triggering complementmediated lysis or antibody-mediated opsonization and phagocytosis of the red blood cells. One form of autoimmune anemia is drug-induced: when certain drugs such as penicillin or the anti-hypertensive agent methyldopa interact with red blood cells, the cells become antigenic. The immunodiagnostic test for autoimmune hemolytic anemias generally involves a , in which the red cells are incubated with an anti–human IgG antiserum. If IgG auto- antibodies are present on the red cells, the cells are agglutinated by the antiserum. Goodpasture’s Syndrome In Goodpasture’s syndrome, auto-antibodies specific for certain basement-membrane antigens bind to the basement membranes of the kidney glomeruli and the alveoli of the lungs. Subsequent complement activation leads to direct cellular damage and an ensuing inflammatory response mediated by a buildup of complement split products. Damage to the glomerular and alveolar basement membranes leads to progressive kidney damage and pulmonary hemorrhage. Death may ensue within several months of the onset of symptoms. Biopsies from patients with Goodpasture’s syndrome stained with fluorescent-labeled anti-IgG and anti- C3b reveal linear deposits of IgG and C3b along the basement Membranes. Insulin-Dependent Diabetes Mellitus A disease afflicting 0.2% of the population, insulin-dependent diabetes mellitus (IDDM) is caused by an autoimmune attack on the pancreas. The attack is directed against specialized insulin-producing cells (beta cells) that are located in spherical clusters, called the islets of Langerhans, scattered throughout the pancreas. The autoimmune attack destroys beta cells, resulting in decreased production of insulin and consequently increased levels of blood glucose. Several factors are important in the destruction of beta cells. First, activated CTLs migrate into an islet and begin to attack the insulinproducing cells. Local cytokine production during this response includes IFN-_, TNF-_, and IL-1. Auto-antibody production can also be a contributing factor in IDDM. The first CTL infiltration and activation of macrophages, frequently referred to as insulitis, is followed by cytokine release and the presence of auto-antibodies, which leads to a cell-mediated DTH response. The subsequent beta-cell destruction is thought to be mediated by cytokines released during the DTH response and by lytic enzymes released from the activated macrophages. Auto-antibodies to beta cells may contribute to cell destruction by facilitating either antibody-plus- complement lysis or antibody-dependent cell-mediated cytotoxicity (ADCC). The abnormalities in glucose metabolism that are caused by the destruction of islet beta cells result in serious metabolic problems that include ketoacidosis and increased urine production. The late stages of the disease are often characterized by atherosclerotic vascular lesions—which in turn cause gangrene of the extremities due to impeded vascular flow— renal failure, and blindness. If untreated, death can result. The most common therapy for diabetes is daily administration of insulin. This is quite helpful in managing the disease, but, because sporadic doses are not the same as metabolically regulated continuous and controlled release of the hormone, periodically injected doses of insulin do not totally alleviate

41 BT6602/Immunology Department of Biotechnology 2018-2019 the problems caused by the disease. Another complicating feature of diabetes is that the disorder can go undetected for several years, allowing irreparable loss of pancreatic tissue to occur before treatment begins. Some Autoimmune Diseases Are Mediated by Stimulating or Blocking Auto-Antibodies In some autoimmune diseases, antibodies act as agonists, binding to hormone receptors in lieu of the normal ligand and stimulating inappropriate activity. This usually leads to an overproduction of mediators or an increase in cell growth. Conversely, auto-antibodies may act as antagonists, binding hormone receptors but blocking receptor function. This generally causes impaired secretion of mediators and gradual atrophy of the affected organ. Graves’ Disease The production of thyroid hormones is carefully regulated by thyroid-stimulating hormone (TSH), which is produced by the pituitary gland. Binding of TSH to a receptor on thyroid cells activates adenylate cyclase and stimulates the synthesis of two thyroid hormones, thyroxine and triiodothyronine. A patient with Graves’ disease produces auto-antibodies that bind the receptor for TSH and mimic the normal action of TSH, activating adenylate cyclase and resulting in production of the thyroid hormones.Unlike TSH, however, the autoantibodies are not regulated, and consequently they overstimulate the thyroid. For this reason these auto-antibodies are called long-acting thyroid-stimulating (LATS) antibodies Myasthenia Gravis Myasthenia gravis is the prototype autoimmune disease mediated by blocking antibodies. A patient with this disease produces auto-antibodies that bind the acetylcholine receptors on the motor end-plates of muscles, blocking the normal binding of acetylcholine and also inducing complement mediated lysis of the cells. The result is a progressive weakening of the skeletal muscle. Ultimately, the antibodies destroy the cells bearing the receptors. The early signs of this disease include drooping eyelids and inability to retract the corners of the mouth, which gives the appearance of snarling. Without treatment, progressive weakening of the muscles can lead to severe impairment of eating as well as problems with movement. However, with appropriate treatment, this disease can be managed quite well and afflicted individuals can lead a normal life.

Systemic Autoimmune Diseases Systemic Lupus Erythematosus One of the best examples of a systemic autoimmune disease is systemic lupus erythematosus (SLE), which typically appears in women between 20 and 40 years of age; the ratio of femaleto male patients is 10:1. SLE is characterized by fever, weakness, arthritis, skin rashes, pleurisy, and kidney dysfunction. Lupus is more frequent in African-American and Hispanic women than in Caucasians, although it is not known why this is so. Affected individuals may produce autoantibodies to a vast array of tissue antigens, such as DNA, histones, RBCs, platelets, leukocytes, and clotting factors; interaction of these auto-antibodies with their specific antigens produces various symptoms.Auto-antibody specific for RBCs and platelets, for example, can lead 42 BT6602/Immunology Department of Biotechnology 2018-2019 to complement-mediated lysis, resulting in hemolytic anemia and thrombocytopenia, respectively. When immune complexes of auto-antibodies with various nuclear antigens are deposited along the walls of small blood vessels, a type III hypersensitive reaction develops. The complexes activate the complement system and generate membrane-attack complexes and complement split products that damage the wall of the blood vessel, resulting in vasculitis and glomerulonephritis. Excessive complement activation in patients with severe SLE produces elevated serum levels of the complement split products C3a and C5a, which may be three to four times higher than normal. C5a induces increased expression of the type 3 complement receptor (CR3) on neutrophils, facilitating neutrophil aggregation and attachment to the vascular endothelium. As neutrophils attach to small blood vessels, the number of circulating neutrophils declines () and various occlusions of the small blood vessels develop (vasculitis). These occlusions can lead to widespread tissue damage. Laboratory diagnosis of SLE focuses on the characteristic antinuclear antibodies, which are directed against doublestranded or single-stranded DNA, nucleoprotein, histones, and nucleolar RNA. Indirect immunofluorescent staining with serum from SLE patients produces various characteristic nucleus-staining patterns. Multiple Sclerosis Multiple sclerosis (MS) is the most common cause of neurologic disability associated with disease in Western countries. The symptoms may be mild, such as numbness in the limbs, or severe, such as paralysis or loss of vision.Most people with MS are diagnosed between the ages of 20 and 40. Individuals with this disease produce autoreactive T cells that participate in the formation of inflammatory lesions along the myelin sheath of nerve fibers. The cerebrospinal fluid of patients with active MS contains activated T lymphocytes, which infiltrate the brain tissue and cause characteristic inflammatory lesions, destroying the myelin. Since myelin functions to insulate the nerve fibers, a breakdown in the myelin sheath leads to numerous neurologic dysfunctions.Certainly some viruses can cause demyelinating diseases, and it is tempting to speculate that virus infection plays a significant role in MS, but at present there is no definitive data implicating a particular virus. Rheumatoid Arthritis Rheumatoid arthritis is a common autoimmune disorder, most often affecting women from 40 to 60 years old. The major symptom is chronic inflammation of the joints, although the hematologic, cardiovascular, and respiratory systems are also frequently affected. Many individuals with rheumatoid arthritis produce a group of auto-antibodies called rheumatoid factors that are reactive with determinants in the Fc region of IgG. The classic rheumatoid factor is an IgM antibody with that reactivity. Such auto-antibodies bind to normal circulating IgG, forming IgM-IgG complexes that are deposited in the joints. These immune complexes can activate the complement cascade, resulting in a type III hypersensitive reaction,which leads to chronic inflammation of the joints. Proposed Mechanisms for Induction of Autoimmunity A variety of mechanisms have been proposed to account for the T-cell–mediated generation of autoimmune diseases. Evidence exists for each of these mechanisms and it is likely that autoimmunity does not develop from a single event but rather from a number of different events. In addition, susceptibility to many autoimmune diseases differs between the two sexes. As noted earlier, Hashimoto’s thyroiditis, systemic lupus erythematosus,multiple sclerosis, rheumatoid arthritis, and scleroderma preferentially affect women. Factors that have been proposed to account for this preferential susceptibility, such as hormonal differences between the sexes and the potential effects of fetal cells in the maternal circulation during pregnancy, are discussed in the Clinical Focus.

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