T cell mediated immunity Topics T cell mediated immunity Overview Antigen presenting cells Co-stimulation Maturation of APC Interleukine 2 (IL 2) Clonal expansion 11/27/2018 MICR 415 / 515 / 682
Development in the thymus Naive T cells Blood Peripheral lymphoid tissue Immunological memory Ag (APC) Armed effector T cells (Rapid action) Target Cells Primary cell-mediated immune response 11/27/2018 MICR 415 / 515 / 682
Cell – Cell interactions in the Lymph Node Ag T cells enter lymph node T cells monitor APC Fig 8.2 If no interaction, T cells leave If interaction, T cells proliferate and differentiate 11/27/2018 MICR 415 / 515 / 682
Pathogen products are transported to peripheral lymphoid tissues Peripheral sites to draining lymph nodes Blood to Spleen Mucosal surfaces to Peye’s Patches (MALT) T cells Enter via High endothelial venules Have contact with APC (Sample MHC) Receive survival signals If not activated they exit back into circulation 11/27/2018 MICR 415 / 515 / 682
Cytotoxic T lymphocytes Types of T cells Cytotoxic T lymphocytes CD8+ TCR recognizes MHC I endogenous peptide Killing of self cells infected with virus tumor cells Helper T lymphocytes (T helper cells) CD4+ TCR recognizes MHC II exogenous peptide Production of cytokines Activation of macrophages Immune response regulation 11/27/2018 MICR 415 / 515 / 682
Antigen Presenting cells Macrophages Scavengers – innate immune response Can present antigens in MHC I and II and provide co-stimulation when activated Immature cells reside in the tissues i.e Langerhans’ ( low MHC expression, high phagocytic activity) Upon activation by infection they migrate to lymphoid organs (high MHC expression, no phagocytic activity) Dendritic Cells B cells Bind to pathogens through surface receptors Display peptides in MHC II Express co-stimulatory molecules in response to stimuli by infection or cytokines Antigen Presenting cells Fig 8.3 11/27/2018 MICR 415 / 515 / 682
Cell adhesion molecules stabilize cell-cell interactions SELECTINS Leukocyte homing Fig 8.4 11/27/2018 MICR 415 / 515 / 682
Cell adhesion molecules stabilize cell-cell interactions INTEGRINS Leukocyte homing & Cell activation 11/27/2018 MICR 415 / 515 / 682
Adhesion molecules stabilize cell-cell interactions 11/27/2018 MICR 415 / 515 / 682
Priming Co-stimulation 11/27/2018 MICR 415 / 515 / 682
Co-stimulation 11/27/2018 MICR 415 / 515 / 682
Co-stimulation Fig 8.12 11/27/2018 MICR 415 / 515 / 682
Improper Co-stimulation 11/27/2018 MICR 415 / 515 / 682
Activation only by professional APC Activated Anergy Fig 8.13 11/27/2018 MICR 415 / 515 / 682
Maturation of Dendritic cells 11/27/2018 MICR 415 / 515 / 682 Fig 8.14
11/27/2018 MICR 415 / 515 / 682
11/27/2018 MICR 415 / 515 / 682
11/27/2018 MICR 415 / 515 / 682
B cell Ag presentation 11/27/2018 MICR 415 / 515 / 682
11/27/2018 MICR 415 / 515 / 682
11/27/2018 MICR 415 / 515 / 682
Naïve T cells are small resting cells that have long lives High affinity IL-2 receptor Naïve T cells are small resting cells that have long lives Infrequent divisions Infrequent apoptosis Upon activation, T cells enter cell cycle, divide and proliferate Process mediated by IL-2 11/27/2018 MICR 415 / 515 / 682
Co-stimulation leads to IL-2 expression Low affinity IL-2 receptor IL-2 High affinity IL-2 receptor 11/27/2018 MICR 415 / 515 / 682
Naive T cells Activated T cells No need for co-stimulation Clonal expansion Naive T cells Activated T cells No need for co-stimulation Fig 8.22 11/27/2018 MICR 415 / 515 / 682
Cell-surface Molecule expression changes with activation of T cell 11/27/2018 MICR 415 / 515 / 682