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Immunology: Antibody Basics 2

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John A. Burns School of Medicine JABSOM e-Learning for Basic Sciences e-Learning To navigate: 1 1. Yellow navigation bar 2 Immunology: Antibody Basics 2. Back and Fwd buttons Estimated Learning Time: 30 min. 3 4 Back Fwd 5 One :: General Structure 6 7 Identify the Parts of an Antibody 8 Two :: Isotypes 9 Identify Antibody Isotypes 10 [ Start Now! ] 11 Three :: Function 12 Match Antibody Functions With Isotypes 13 14 Four :: Diversity 15 Explain Antibody Diversity 16 17 Antibody 18 Advice 19 20 21 Allow Hi! 22 me to be your Ctrl + L 23 Command + L guide... find me 24 FULL SCREEN at the bottom 25 in Adobe Acrobat of each page! 26 Contributors William L. Gosnell, Ph.D. Software Requirements: Kenton J. Kramer, Ph.D. Click to download Karen M. Yamaga, Ph.D. the latest versions Department of Tropical Medicine, Medical Microbiology and Pharmacology JABSOM John A. Burns School of Medicine e-Learning e-Learning for Basic Sciences OVERVIEW 1 2 3 Contents 4 5 instructional By the end of this module you should be This One :: General Structure 6 module was designed with you able to: Identify the Parts of an Antibody Page 3 7 in mind. Understanding antibody 1. Identify the parts of an antibody. basics will help you understand 2. Identify antibody isotypes. Two :: Isotypes 8 immunology concepts that are 3. Match antibody functions with isotypes. Identify Antibody Isotypes Page 9 9 necessary to pass USMLE board 4. Explain antibody diversity from 10 exams - the first step on your way somatic recombination. to becoming a doctor. Three :: Function 11 Please start with Section One... Match Antibody Functions With Isotypes Page 13 12 Four :: Diversity Page 19 13 Explain Antibody Diversity 14 15 16 17 18 19 20 Acknowledgements 21 John A. Burns School of Medicine College of Education Ctrl + L 22 Department of Tropical Medicine, Department of Educational Command + L 23 Medical Microbiology & Pharmacology Office of Medical Education Technology Sandra P. Chang, Ph.D. Richard T. Kasuya, M.D., M.S.Ed. Catherine P. Fulford, Ph.D. FULL SCREEN 24 William L. Gosnell, Ph.D. Joshua L. Jacobs, M.D. Ariana Eichelberger, M.Ed. in Adobe Acrobat Kenton J. Kramer, Ph.D. Gwen S. Naguwa, M.D. 25 Leslie Q. Tam, Ph.D. Marlene Lindberg, Ph.D. 26 Karen M. Yamaga, Ph.D. Hi folks! Before you start... use the FULL SCREEN view to maximize the experience. Click the Fwd button to advance... Back Fwd JABSOM John A. Burns School of Medicine e-Learning e-Learning for Basic Sciences 1 2 3 4 5 6 7 8 CHAPTER ONE 9 10 11 GENERAL STRUCTURE 12 13 14 15 16 17 Objective: Identify the Parts of an Antibody 18 19 20 21 22 23 24 25 26 Back Fwd JABSOM John A. Burns School of Medicine e-Learning e-Learning for Basic Sciences ONE GENERAL STRUCTURE 1 2 3 4 Overview 5 Also known as immunoglobulins (abbreviated as Ig), 6 antibodies are molecules found in blood 7 and bodily fluids of humans and other 8 vertebrates. They are used by the immune system to identify and destroy foreign 9 substances to the body, such as bacteria 10 and viruses. 11 More specifically, antibodies are Y- 12 shaped glycoproteins consisting of four 13 polypeptide chains linked covalently by disulfide bonds (Figure 1). They act as 14 antigen-specific receptors on B-cells, 15 and when secreted by plasma cells, 16 mediate humoral responses. 17 18 19 Figure 1. Basic antibody structure (monomer IgG). 20 Y-shaped molecule formed by four polypeptide 21 chains, indicated by two red and two blue bars. Small dark lines indicate disulfide bonds. 22 23 24 Definition: Antibody - also called immunoglobulin (Ig), a Y-shaped glycoprotein 25 molecule found in human blood or bodily fluids; used by 26 the immune system to find and destroy antigens. We antibodies know how to stay in shape... “Y” shape, that is! See the next page to learn what makes our shape. Back Fwd JABSOM John A. Burns School of Medicine e-Learning e-Learning for Basic Sciences ONE GENERAL STRUCTURE 1 2 1. Heavy & Light Chains 3 4 3. Framework & Hypervariable Antibodies contain two identical 5 heavy chains and two identical Regions 6 light chains. Bonded together 7 by the disulfide bonds, they form The variable region is made up of the Y-shaped molecule (Figure 2). two parts: the framework region and 8 hypervariable region. The framework 9 region is structurally similar. But most 10 2. Variable & Constant Regions importantly, the hypervariable regions are extremely diverse, as the name 11 indicates. This allows for the creation of 12 The heavy and light chains are a wide variety of antibodies, and in turn, subdivided into two regions or 13 allows the immune system to recognize domains: the variable region and protect against a wide variety of 14 and constant region. Constant antigens. 15 regions have the same amino acid sequences, while variable regions Antigen specificity is determined by the 16 have different amino acid sequences. amino acids in the hypervariable regions. 17 Variable regions are responsible for 18 antigen recognition and binding. 19 20 Figure 2. Basic antibody structure (monomer IgG). Red and blue areas indicate light 21 and heavy chains respectively. Light and dark areas of each chain indicate the variable and constant regions respectively. Small dark lines indicate disulfide bonds. 22 23 24 Synonyms: Region = Domain 25 Hypervariable Region = Complementarity Determining Region (CDR) 26 Just like human beings, our “anatomy” is very similar Back Fwd and yet we are so diverse - keep this in mind as we progress... JABSOM John A. Burns School of Medicine e-Learning e-Learning for Basic Sciences ONE GENERAL STRUCTURE 1 2 3 4 QUICK REVIEW Think 5 6 Fast! 7 Answer these quick questions 8 before you move on... 9 10 11 4. Referring to the antibody diagram, the hypervariable region is found in 12 1. An antibody: letter: 13 a. avoids antigen contact. 2. Referring to the antibody diagram, a. (a) 14 b. has one disulfide bond. the light and heavy chains are indicated by letters: b. (b) 15 3. Referring to the antibody diagram, c. has only two polypeptide chains. 16 a. (a) and (b) respectively the variable and constant regions c. (c) d. is a glycoprotein. b. (a) and (c) respectively are indicated by letters: d. (d) 17 18 c. (b) and (d) respectively a. (a) and (b) respectively 19 d. (c) and (d) respectively b. (a) and (c) respectively c. (b) and (d) respectively 20 d. (c) and (d) respectively 21 22 23 24 25 26 Did you get them all correct? Good! Let’s move on to the last section on General Structure... Back Fwd JABSOM John A. Burns School of Medicine e-Learning e-Learning for Basic Sciences ONE GENERAL STRUCTURE 1 2 4. Proteolytically Derived 3 Fragments of IgG 4 5 Antibodies can be broken down PEPSIN-DIGESTED FRAGMENTS PAPAIN-DIGESTED FRAGMENTS 6 (proteolysis) into different fragments by two common enzymes. 7 8 Pepsin is a digestive protease created by stomach cells that degrade food 9 proteins. Papain is a cysteine protease, 10 commonly found in papaya, also can 11 digest proteins. As a result of using either, the protein-based antibodies can 12 be broken into fragments. 13 The tips of the Fab region, composed of 14 heavy and light chains, are responsible 15 for recognizing and binding to foreign objects. At the base of the antibody 16 is the Fc region, composed of two 17 heavy chains, and by binding to specific 18 proteins ensures that the appropriate 19 immune response is generated. Figure 3. Proteolytically derived fragments of an antibody (monomer IgG) from pepsin and papain. On the 20 Figure 2 illustrates the fragments created left, the action of pepsin results in one large F(ab’)2 fragment and many different low molecular weight when pepsin and papain digest antibody peptide fragments. On the right, the action of papain results in two Fab fragments and one Fc fragment. 21 IgG. 22 23 24 Definitions: Proteolysis - the breakdown of proteins into peptides and amino acids; IgG - an immunoglobulin (Ig) isotype with a gamma (G) heavy chain; 25 Proteolytically (adj.) the most common antibody isotype 26 Like a surgeon’s scalpel, pepsin and papain cuts us apart. It’s not exactly a “Nip/Tuck” cosmetic procedure... Back Fwd JABSOM John A. Burns School of Medicine e-Learning e-Learning for Basic Sciences ONE GENERAL STRUCTURE 1 2 3 4 QUICK REVIEW Think 5 6 Fast! 7 Answer these quick questions 8 before you move on... 9 10 4. Referring to the antibody diagrams, 11 the fragments caused by the actions 2. Pepsin and papain are of pepsin and papain are: 12 a. antibody fragments. a. (a) and (b); (c) and (d) 13 b. digestive enzymes. respectively. 14 c. fragments that form antibodies. b. (a) and (d); (c) and (b) 15 3. Referring to the antibody diagrams, respectively. 1. Proteolysis of an antibody is when 16 d. molecules that split disulfide the F(ab’) , Fab, and Fc fragment a. an enzyme fragments an 2 c. (b) and (c); (a) and (d) bonds. are: 17 antibody. respectively. a. (a), (b) and (c) respectively 18 b. its disulfide bonds split. d. (c) and (d); (a) and (b) b. (a), (b) and (d) respectively respectively. 19 c. its light chains are separated 20 from the heavy chains c. (a), (c) and (d) respectively 21 d. protein fragments form an d. (b), (c) and (d) respectively antibody. 22 23 24 25 26 Now that you know how we antibodies are structured, Let’s move on..
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