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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. Adaptive Immunity.
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Principles of ImmunologyOverview of Adaptive Immunity1/24/06 “Too many people overvalue what they are not and undervalue what they are.” M Forbes
Adaptive Immunity • Specific host defenses that are mediated by B and T lymphocytes following exposure to antigens, and exhibit diversity and memory.
Word List • Clonal selection • CD 4 • CD 8 • Epitope • Endogenous antigen • Exogenous antigen • Phagolyzosome
Characteristics of Adaptive Immunity • Antigenic specificity • Diversity • Immunologic memory • Self recognition
Interface with Innate Immune System • Phagocytosis • Inflammation
Major Cells of Adaptive Immunity • Lymphocytes • B • T • TH • TC • Antigen presenting cells (APCs) • Dendritic cells • Macrophage • B lymphocytes
B Lymphocytes • Originate and mature in bone marrow • Membrane bound antibody • Ag binding triggers division and differentiation • Progeny • Plasma cells • Memory B cells
T Lymphocytes • Mature in thymus • T cell receptors • MHC restriction • Class I • Nucleated cells • Reacts with CD8 • Class II • APCs • Reacts with CD4
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
Antigen Presenting Cells • Dendritic cells • MHC I and II on surface • Ag is internalized • Stimulates T-helper cells • Macrophages • B lymphocytes
Humoral Immunity • Conferred via serum (cell-free) • Antibody dependent • Antibody functions • Enhanced elimination • Neutralization • C fixation/lysis
Cell-mediated Immunity • Conferred via lymphocyte exchange • Cell dependent • Modulates humoral immunity • Cytotoxic
Antigen Recognition • Epitopes • B cells recognize epitopes alone • T cells require MHC association • Major molecules involved • Membrane bound antibody • TCR • MHC I • MHC II
Lymphocyte Diversity • Random rearrangement of gene segments • 1010 potential specificities • “Mature” lymphocytes are said to be “committed”
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
Clonal Selection • Occurs in Secondary lymphoid organs • Specificity of all progeny is identical • Explains secondary response • Memory cells more numerous than naïve cells