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29 Cards in this Set
- Front
- Back
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What is the earliest Ig produced?
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IgM (B-cell receptor)
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What are the charac of IgM? Function?
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Monomer receptor on B-cells. Similar to Ig G
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What is the most prevalent Ig in serum?
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IgG (IgG1-4)
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What are the charac of IgG?
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Only Ig that can cross placenta. Inactivates toxins & virsus, promotes phago, activates complement
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What is the most prevalent Ig in secretion?
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IgA (IgA1-2)
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What is the fcn of IgA?
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Immunity in the gut & on other mucus membranes
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Which Ig is the antigen receptor on B-cells?
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IgD
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What is the fcn of IgD?
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Antigen receptor
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Which Ig mediates immediate hypersensitivity; allergy?
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IgE (absorbs to mast cells & basophils)
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Describe antibody structure?
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2 heavy & 2 light chains held together by disulfide bonds, symmetrical, constant & variable regions (Cl, Ch, Vl, Vh), hypervariable regions, 2 antigen binding sites, & hinge region
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What determines antibody specificity?
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Amino acid sequence
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What are hypervariable regions?
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Complementarity determining regions (CDR)= point of most intimate contact w/ antigen
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How does Papain cleave antibody?
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cleaves @ the hinge region-> 2 Fab fragment (w/ antigen binding sites) & 1 Fc fragment (w/ Ch)
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How does Pepsin cleave antibody?
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Digests Fc into smaller fragments & leaves 1 F(ab') w/ two antigen binding sites
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What are the charac of Fc fragment?
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Binds Fc receptor on macrophages, NK cells, & mast cells. Embedded in membrane as Ag receptor, site of complement action, & interaction dite for crossing placenta
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Describe the secondary structure of antibody?
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2 L chain domains (Vl & Cl) & 4-5 H chain domains (Vh, Ch1, Ch2, Ch3, & Ch4 in IgM/IgE)
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What are the antigenic determinants on Ig?
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Isotype, Allotype, & Idiotype
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What is isotype?
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H chain determinants unique to Ig class (mu, gamma, alpha, delta, epsilon), Ig subclass determinants (a1, y2, y3, y4, a1, a2), L chain determinants (k & lambda)
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What is Allotype?
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Useful in studying inheritance
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What is Idiotype?
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Unique config of antigen binding site
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Describe variable heavy chain genetic recombination.
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D+J-> V+DJ. VDJ is conserved. Transcribed to RNA (VDJ+C)->splicing
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How do light chains recombine?
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Rearranges independently
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How is antibody diversity generated?
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Jcnal diversity, N-region additions, somatic mutations, well over 10^9specificities, & allelic exclusion
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What is allelic exclusion?
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Guarantees that each B-cell expresses one antigen specificity
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What Ig are expressed together?
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IgD & M
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What is gene switching?
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Upon activation DNA genes recombine; VDJ combines w/ C @ switch region-> intervening genes are lost-> cell makes IgG1-> as RNA decays it loses IgM & D. *Doesn't change specificity. Only alters DNA after Ag stim
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What is the structural arrangement of IgM as B-cell receptor & secreted form?
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Receptor= monomer. Secreted= pentamer w/ J chains
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What is the structural arrangement of IgA in secreted form?
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Monomer or Dimer w/ J chain (tail to tail)
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What are the important charac of IgG that distinguishes it from other Ig?
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Longest half life (25-35), mostly in serum, Only one that crosses placenta
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