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Microbiology Chapter 17 Outline

The Adaptive (p. 469) 1. Adaptive is the body’s ability to react specifically to a microbial infection. 2. The body’s response to the first contact with an is called the primary response. 3. Subsequent contact with the same antigen results in a secondary or memory response to that antigen.

Dual Nature of the (pp. 469–470) 1. involves , which are found in serum and and are produced by B cells. 2. that mature in red marrow become B cells. 3. Cellular immunity involves T cells. 4. Lymphocytes that migrate through the become T cells. 5. receptors recognize presented on MHC. 6. Cellular immunity responds to intracellular antigens; humoral immunity responds to antigens in body fluids.

Cytokines: Chemical Messengers of Immune Cells (pp. 470–471) 1. Cells of the immune system communicate with each other by means of chemicals called . 2. (IL) are cytokines that serve as communicators between leukocytes. 3. cause leukocytes to migrate to an infection. 4. Some interferons stimulate the ; others protect cells against . 5. Tumor necrosis factor promotes the inflammatory reaction. 6. Hematopoietic cytokines promote development of white cells. 7. Overproduction of cytokines leads to a storm, which results in tissue damage.

Antigens and Antibodies (pp. 471–479) Antigens (pp. 471–472) 1. An antigen (or ) is a chemical substance that causes the body to produce specific antibodies. 2. As a rule, antigens are or large polysaccharides. Antibodies are formed against specific regions on antigens called , or antigenic determinants. 3. A is a low-molecular-weight substance that cannot cause the formation of antibodies unless combined with a carrier molecule; react with their antibodies independently of the carrier molecule. Microbiology Chapter 17 Outline

Antibodies (pp. 472–475) 4. An , or immunoglobulin, is a produced by B cells in response to an antigen and is capable of combining specifically with that antigen. 5. Typical monomers consist of four polypeptide chains: two heavy chains and two light chains. 6. Within each chain is a variable (V) region that binds the and a constant (C) region that distinguishes the different classes of antibodies. 7. An antibody monomer is Y-shaped or T-shaped: the V regions form the tips; the C

regions form the base and FC (stem) region.

8. The FC region can attach to a host cell or to complement. 9. IgG antibodies are the most prevalent in serum; they provide naturally acquired , neutralize bacterial toxins, participate in complement fixation, and enhance phagocytosis. 10. IgM antibodies consist of five monomers held by a joining chain; they are involved in agglutination and complement fixation. 11. Serum IgA antibodies are monomers; secretory IgA antibodies are dimers that protect. mucosal surfaces from invasion by pathogens. 12. IgD antibodies are on B cells; they may delete B cells that produce antibodies against self. 13. IgE antibodies bind to mast cells and and are involved in allergic reactions.

Humoral Immunity Response Process (pp. 475–477)

1. B cells have antibodies on their surfaces, which recognize specific epitopes. 2. For T-independent antigens: B cells are selected by free antigens. 3. For T-dependent antigens: the B cell’s immunoglobulins combine with an antigen, and the

antigen fragments combined with MHC class II activate TH cells. The TH cells activate a B cell. 4. Activated B cells differentiate into plasma cells and memory cells. 5. Plasma cells produce IgM antibodies and then produce other classes, usually IgG. 6. B cells that recognize self are eliminated by . 7. Immunoglobulin genes in B cells recombine so that mature B cells each have different genes for the V region of their antibodies.

Microbiology Chapter 17 Outline

Antigen–Antibody Binding and Its Results (pp. 477–479) 1. An antigen–antibody complex forms when an antibody binds to its specific epitopes on an antigen. 2. Agglutination results when an antibody combines with epitopes on two different cells. 3. Opsonization enhances phagocytosis of the antigen. 4. Antibodies that attach to microbes or toxins and prevent them gaining access to the host or performing their action cause neutralization. 5. Complement activation results in cell lysis.

Cellular Immunity Response Process (pp. 479–484) 1. T cells mature in the thymus gland. Thymic selection removes T cells that don’t recognize MHC molecules of the host and T cells that will attack host cells presenting self-proteins in MHC. 2. Helper T cells recognize antigens processed by antigen-presenting cells and presented in MHC II. 3. Cytotoxic T cells recognize antigens processed by all host cells and presented in MHC I.

Antigen-Presenting Cells (APCs) (p. 480) 4. APCs include B cells, dendritic cells, and . 5. Dendritic cells are the primary APCs. 6. Activated macrophages are effective and APCs. 7. APCs carry antigens to lymphoid tissues where T cells that recognize the antigen are located.

Classes of T Cells (pp. 480–484) 8. T cells are classified according to their functions and cell-surface glycoproteins called CDs. + 9. T helper (CD4 T) cells differentiate into TH1 cells, which are involved in cellular immunity;

TH2 cells, which are involved in humoral immunity and are associated with allergic reactions

and parasitic infections; and TH17 cells, which activate innate immunity.

10. T regulatory cells (Treg) suppress T cells against self. 11. Cytotoxic lymphocytes (CTLs), or CD8+ T cells, are activated by endogenous antigens and MHC class I on a target cell and are transformed into effector and memory CTLs. 12. CTLs lyse or induce apoptosis in the target cell.

Microbiology Chapter 17 Outline

Extracellular Killing by the Immune System (p. 484) 1. Natural killer (NK) cells lyse -infected cells, tumor cells, and parasites. They kill cells that do not express MHC class I antigens.

Antibody-Dependent Cell-Mediated Cytotoxicity (pp. 484–485) 1. In antibody-dependent cell-mediated ctotoxicity (ADCC), NK cells and macrophages lyse antibody-coated cells.

Immunological Memory (pp. 485–486) 1. The relative amount of antibody in serum is called the antibody titer. 2. The peak IgG titer in the primary response occurs 10–17 days after exposure to an antigen. 3. The peak titer in the secondary response occurs 2–7 days after exposure.

Types of Adaptive Immunity (pp. 486–488) 1. Immunity resulting from infection is called naturally acquired active immunity; this type of immunity may be long-lasting. 2. Antibodies transferred from a mother to a fetus (transplacental transfer) or to a newborn in colostrum results in naturally acquired passive immunity in the newborn; this type of immunity can last up to a few months. 3. Immunity resulting from vaccination is called artificially acquired active immunity and can be long-lasting. 4. Artificially acquired passive immunity refers to humoral antibodies acquired by injection; this type of immunity can last for a few weeks. 5. Serum containing antibodies is often called antiserum. 6. When serum is separated by gel electrophoresis, antibodies are found in the gamma fraction of the serum and are termed immune serum globulin, or gamma globulin.