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The Humoral (B cell) Immune Response

The Humoral (B cell) Immune Response. Linked Recognition. Th2 focus their activating cytokines… (Talin binds to actin microfilaments). Antibody isotype switching:. Switch transcripts produced on both chromosomes. Where do activated B cells and activated helper T cells get together?

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The Humoral (B cell) Immune Response

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  1. The Humoral (B cell) Immune Response

  2. Linked Recognition

  3. Th2 focus their activating cytokines… (Talin binds to actin microfilaments)

  4. Antibody isotype switching:

  5. Switch transcripts produced on both chromosomes

  6. Where do activated B cells and activated helper T cells get together? (trapping) Freq of lympho’s specific for given Ag is 1/1,000,000

  7. Some B cells in the primary focus become plasma cells

  8. Other B cells form germinal centers • Somatic hypermut’n • Affinity maturation • Isotype switching

  9. FDCs attract B cells to germinal centers

  10. B cells undergo somatic hypermutation, selection (+ and -) • 1 bp change per 1000 bp per cell division • V regions 360 bp • ¾ of changes is an altered aa • ½ of B cells gets changed BCR

  11. B cell survival in Germinal Centers • Cross-linking of BCRs by Ag • Ag on FDCs??? • Pathogens multiplying in lymphoid tissue??? • CD40 ligation by T cell CD40L • Other signals? • Eg. TNF family cytokines

  12. Thymus-independent 1 Ags (TI-1) • Induce all B cell division • Called B cell mitogens • Eg. LPS • Unable to induce isotype switching(?), affinity maturation, or memory cells

  13. TI-2 Ags • Activate only mature B cells • Repeating epitopes • IgM, sometimes IgG • Eg. Bacterial capsular polysaccharides, pyogenic bacteria

  14. Transcytosis of IgA • Gut, lungs, tears, saliva, mammary • Poly-Ig Rc • Protection of epithelial surfaces

  15. IgG and IgA can inhibit viral infectivity

  16. IgM has two conformations

  17. Ag-bound Ab binds FcRc with high avidity

  18. Fc and C3b Rc’s on phagocytes

  19. Schistomsome larva attacked by eosinophils

  20. ADCC = antibody- dependent cell-mediated cytotoxicity

  21. IgE pre-loaded on mast cells • Cross-linking causes mediator release • Prostaglandin D2, leukotriene C4, TNF-alpha

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