lecture 5 antibody

lecture 5 antibody - Antibody Structure and the Generation...

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Antibody Structure and the Generation of B-Cell Diversity Lecture 5 Chapter 4 MMI 188 Human Immunology José V. Torres, Ph.D. Professor Medical Microbiology and Immunology School of Medicine University of California at Davis jvtorres@ucdavis.edu
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Function of antibodies: To combat infection • Several different mechanisms • Neutralization • Opsonization • Immunoglobulins = antigen-binding molecules made by B cells • Antibody = the secreted form of an immunoglobulin B cells have membrane-bound Ig on their surface When B cells encounter antigen, they differentiate to plasma cells Plasma cells secrete antibody but do not have Ig on their surface
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Antibodies produced by plasma cells clear extracellular pathogens and their toxins best source of protective immunity antibody repertoire: 10 9 specificity of the secreted antibody is the same as that of the B cell receptor
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The IgG Molecule two identical heavy chains two identical light chains carbohydrates attached to heavy chains variable region constant region flexible hinge Structure 4 polypeptide chains (2 heavy, 2 light) Connected by covalent (S-S) and non- covalent bonds Divalent: 2 antigen-binding sites Repeating globular domains C-terminal domains are Constant (C) N-terminal domains are Variable (V)
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Protease cleavage reduction of disulfide bonds Papain digestion: 2 Fab fragments (A ntigen B inding) one Fc subunit (C onstant region)
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IgG molecule has flexible hinge
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Heavy chains: IgM pentamer IgG IgA monomer and dimer IgE IgD Light chains: kappa κ lambda λ Human Immunoglobulin Classes Differences: •heavy chain C region length •location of disulfide bonds •carbohydrate groups •hinge region in IgG, IgA and IgD •no hinge region in IgM and IgE
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Major Classes of Antibodies IgM – Pentamer; First antibody made after infection – Can bind complement; Cannot bind Fc receptors on phagocytes IgG – After acute infection, IgG becomes the dominant antibody in
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lecture 5 antibody - Antibody Structure and the Generation...

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