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Flashcards in Humoral Immune Response I Deck (18)
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the principal defense mechanism of the humoral adpative immune response is against _____

the principal defense mechanism of the humoral adpative immune response is against microbes with capsule rich in polysaccharides and lipids


contrast the thymus-dependent antigens (TD) and the thymus-independent antigens (TI)

  • thymus-dependent antigens: proteins antigens processed in APCs and recognized by helper T cells
    • help B cell activation
    • heavy chain isotope switching
    • affinity maturation
    • protein antigens with no helper T cell:
      • weak or no antibody resposne
  • thymus-independent antigens: non-protein antigens
    • little isotype-switching
    • little affinity maturation


describe the subset of B-cells found in the spleen and other lymphoid organs vs those found in mucosal tissues and peritoneal cavity


describe the major responders to TD vs TI antigens


describe the role of the spleen in the induction of the humoral response


describe the role of the lymph node in the induction of the humoral response


germinal centers arise within _____ after initial exposure to thymus-dependent antigen in lymph nodes

what are the 3 events in the germinal center?


germinal centers arise within 7-10 days after initial exposure to thymus-dependent antigen in lymph nodes

  • 3 events:
    • affinity maturation
      • result of somatic hypermuation
    • class switching
    • formation of plasma and memory B-cells


describe signal 1 involved in B-cell activation

  • membrane bound antibody have short cytoplasmic tails
    • too short to generate signal by associating with tyrosine kinases and G proteins
  • membrane Ig must be associated with B-cell receptor
    • Ig-a/Ig-B


decribe the co-receptors required in B-cell activation

  • B cell co-receptor
    • complex of 3 proteins
    • CD19: cytoplasmic tail for signal transduction
    • CR2: receptor for C3d (from complement)
    • TAPA-1: transmembrane molecule
  • inhibitory co-receptor
    • CD22: cytoplasmic tail for signal transduction
      • contains ITIM (immunoreceptor tyrosine-based inhibitory motif)


summarize signal 1 and signal 2 in TD-B cell activation


describe the function in Tfh cells in TD-B cell activation

  • T cell expresses CXCR5: draw cells to follicles
  • generation and function of follicular helper T cells (Tfh) depend on costimulatory ICOS
  • secrete IL-21: antibody production (proliferation)
  • in germinal center: class switching and affinity maturation


describe the action of class switching

  • after activation of a mature B cell
  • same variable domains as generated by the process of VDJ recombination but different constant domains in their heavy chain
  • enzyme AID is required
  • dependent on cytokines to switch from IgM to other isotype
    • thymus-dependent antigens
    • interaction of CD40 on B cell and CD40L on T cell
  • X-linked hyper-M syndrome
    • Th cells don't express CD40L, patients only produce IgM
      • no memory cell populations, no germinal centers


describe the function of affinity maturation

  • affinity of antibodies produced in response to a protein antigen increases with prolonged or repeated exposure
  • result of somatic hypermutation of Ig genes (point mutations)
  • followed by selection of high affinity B cells by antigen
  • enzyme activation-induced cytidine deaminase (AID) is required:
    • creates mutations in DNA by deamination of cytosine base


describe the role of the innate immune system in B cell activation (TI)

  • microbes become coated with C3d (product of Factor I on C3b)
  • B-cell have C3d receptor CR2 or CD21
  • engagement enhances antigen-dependent activation of B cells
  • B cells also express Toll-like receptors that can recognize microbial products differently


describe the regulation of the humoral response

  • cytokines play important role
  • antibody feedback
  • antigen-antibody complex forms
  • Fc tail binds to FcγRIIB receptors on B cells
  • inhibition of receptor-mediated B cell activation


contrast the primary vs. secondary humoral response

  • protective antibodies are produced during first (primary) response to a microbe
  • antibodies are produced faster and in larger amounts during subsequent (secondary) responses
  • plasma cells that migrate to bone marrow produce antibodies for years
  • memory cells are also produced that do not produce antibodies


summarize the comparison of primary vs secondary antibody responses


explain why Ig half-life is expanded in neonates