Chapter 8 - Chapter 8 Mature T cells have survived +/Have...

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Mature T cells - have survived +/- - Have unique Ag receptors - Survival signals – MHC & IL-7 - Must have antigen and costimulation o CD28 B7 interaction Types of effector T cells - CD8 cytotoxic T cells – kill virus infected cells. Targets viruses, intracellular bacteria - CD4 Th1 cells – activates infected macrophages, provides help to B cells for antibody production. Targets microbes that persist in macrophage vesicles, extracellular bacteria - CD4 Th2 cells – provides help to B cells for antibody production, aids in class switching to IgE. Targets helminth parasites - CD4 Th17 cells – enhance neutrophil response. Targets extracellular bacteria - CD4 regulatory T cells – suppresses T cell responses Naïve T cells encounter antigen during their recirculation through peripheral lymphoid tissue - T cells enter lymph node cortex from blood via high endothelial venules (HEVs) T cells not activated by antigen presented by dendritic cells exit the lymph node via the cortical sinuses (receive a survival signal through IL-7) T cells activated by antigen proliferate and lose ability to exit lymph node activated T cells differentiate into effectors cells and exit lymph node Antigen specific T cells are detained transiently in the lymph node where they become activated L-selectin and the mucin-like vascular addressins direct naïve lymphocytre homing to lymphoid tissues. - L- selectin – naïve T cells, bind to sialyl-lewis moieties on vascular addressins CD34 and GlyCAM-1 on high endothelial venules in order to enter lymph node o GlyCAM-1 expressed exclusively on high endothelial venules by has no transmembrane region. o CD34 has transmembrane region, and is expressed only on endothelial venule cells. - MAdCAM-1 – expressed on mucosal endothelium and guides entry into mucosal lymphoid tissue. Integrins - heterodimeric proteins containing a B chain (class) and alpha chain (different integrins within a class). Alpha larger than beta, contains binding sites for divalent cations. o LFA-1 – B2 integrin expressed on all T cells. Binds ICAMs o LPAM-1 – on naïve T cells, contributes to mucosal homing by binding with MAdCAM-1 o VLA-4 – B1 integrin that increases expression after T cell activation, binds to VCAM1 Immunoglobulin super family - Bind to LFA-1/VLA-4, other family members. Roles in lymphocyte migration, homing, cell-cell interations Cell Adhesion summary - Adhesion molecules are important for localization, migration, APC interactions - Circulating lymphocyte enters high endothelial venule in lymph node binding of L-selectin to GlyCAM-1 and CD34 allows rolling interaction LFA-1 activated by chemokines bound to ECM activated LFA-1 binds to ICAM-1 lymphocyte migrates to lymph node by diapedesis
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This note was uploaded on 04/17/2008 for the course BIO 4750 taught by Professor Leavey during the Spring '08 term at Georgia Institute of Technology.

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Chapter 8 - Chapter 8 Mature T cells have survived +/Have...

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