Adaptive Immunity (Lecture 16)

MHC & Antigen Processing
1. CLASS I
  1. Endogenous antigen binding
    1. From proteosome degredation
  2. Present antigen to CD8+ T-cells
  3. In cytoplasm
2. CLASS II
  1. Exogenous antigen binding
    1. From phagocytosed bacteria
  2. Outside the cell
  3. Present antigen to CD4+ T-cells
3. Cluster of Differentiation Molecules (CDs)
  1. Used to identify/differentiate
T-Cells
1. Major in B-cell activation
2. T-Cell Receptors (TCRs)
  1. Requires specific antigen to bind
  2. Antigen presentation bridging MHC CLASS II on Antigen Presenting Cell (APC) to TCR on the T-cell
  3. Initiates 1st signaling
    1. MHC I w/CD8
    2. MHC II w/CD4
  4. 2nd signal needed for lymphocute proliferation/differentiation/expression for cytokine genes
3. Naive T-cells until matured by antigen-presentation activation
  1. Proliferate
    1. CD4 T-helpers
    2. CD8 Cytotoxic
4. CD4 T Helper Cells
  1. Activated by antigen-presentation w/MHC II
  2. Th2 help B-cells produce antibodies
    1. Produce specific cytokines
    2. Stimulate antibody responses, defend against helminth parasites
      1. Worms, tapeworms
    3. Allergic reactions
  3. Th1 cells promote cytotoxic activity
    1. Secrete enzymes for lysis & activate macrophages
    2. Mediate inflammation
5. Cytotoxic T-Cells
  1. CD8+ T-cells
    1. Activated by APC on MHC I
      1. Kill target cells w/same antigen-MHC I combo of original activator
        Via perforin pathway
B-Cells
1. Must be activated by specific antigen
  1. Replicate/differentiate into plasma cells (secrete antibodies)
  2. Two mechanisms
    1. T-dependent
      1. More effective for neutraliz. infection & more specific
      2. Reqs. 2 signals for activation
        Antigen-BCR specific int.
        Activated Th2 binds B-cell-presented antigent, secretes B-cell growth factors
        B-cell differenti. into plasma & memory cells
    2. T-independent
      1. Large identical epitopes (like LPS)
      2. Less effective
        Antibodies have low affinity for antigen
        No memory B-cells
2. Immunoglobulic Receptors (specific)
  1. When assoc w/other proteins: B-cell receptors (BCRs)
Antibodies

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Adaptive Immunity (Lecture 16)

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