Humoral Immune Response I Flashcards Preview

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Flashcards in Humoral Immune Response I Deck (18)
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1

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

2

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

3

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

4

describe the major responders to TD vs TI antigens

5

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

6

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

7

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

8

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

9

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)

10

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

11

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

12

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

13

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

14

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

15

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

16

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

17

summarize the comparison of primary vs secondary antibody responses

18

explain why Ig half-life is expanded in neonates