1. Principles of Immunology Overview of Adaptive Immunity 1/24/06 “Too many people overvalue what they are not and undervalue what they are.” M Forbes

2. Adaptive Immunity  Specific host defenses that are mediated by B and T lymphocytes following exposure to antigens, and exhibit diversity and memory.

3. Word List  Clonal selection  CD 4  CD 8  Epitope  Endogenous antigen  Exogenous antigen  Phagolyzosome

4. Characteristics of Adaptive Immunity  Antigenic specificity  Diversity  Immunologic memory  Self recognition

5. Interface with Innate Immune System  Phagocytosis  Inflammation

6. Major Cells of Adaptive Immunity  Lymphocytes B T  T H  T C  Antigen presenting cells (APCs) Dendritic cells Macrophage B lymphocytes

8. B Lymphocytes  Originate and mature in bone marrow  Membrane bound antibody  Ag binding triggers division and differentiation  Progeny Plasma cells Memory B cells

9. T Lymphocytes  Mature in thymus  T cell receptors  MHC restriction Class I  Nucleated cells  Reacts with CD8 Class II  APCs  Reacts with CD4

10. T Lymphocytes(cont’d)  Progeny cells T helper  CD4  Class II restricted  Stimulates B and T cells (helper function) T cytotoxic  CD8  Class I restricted  Further differentiates CTLs(killing function) Memory T cells

11. Antigen Presenting Cells  Dendritic cells MHC I and II on surface Ag is internalized Stimulates T-helper cells  Macrophages  B lymphocytes

12. Humoral Immunity  Conferred via serum (cell-free) Antibody dependent Antibody functions  Enhanced elimination  Neutralization  C fixation/lysis

13. Cell-mediated Immunity  Conferred via lymphocyte exchange Cell dependent Modulates humoral immunity Cytotoxic

15. Antigen Recognition  Epitopes B cells recognize epitopes alone T cells require MHC association  Major molecules involved Membrane bound antibody TCR MHC I MHC II

16. Lymphocyte Diversity  Random rearrangement of gene segments 10 10 potential specificities “Mature” lymphocytes are said to be “committed”

17. Antigen Processing  Exogenous antigens Phagocytosis Degradation Ag peptide/MHC II recognized by T helper  Endogenous antigens Viral or tumor induced Complexes with Class I Recognized by CTLs

18. Clonal Selection  Occurs in Secondary lymphoid organs  Specificity of all progeny is identical  Explains secondary response  Memory cells more numerous than naïve cells