1. T cell mediated immunity
Topics
T cell mediated immunity
Overview
Antigen presenting cells
Co-stimulation
Maturation of APC
Interleukine 2 (IL 2)
Clonal expansion
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2. 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
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3. Cell – Cell interactions in the Lymph NodeAg
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
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4. 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
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5. 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
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6. 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
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7. Cell adhesion molecules stabilize cell-cell interactions SELECTINS
Leukocyte homing
Fig 8.4
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8. Cell adhesion molecules stabilize cell-cell interactions INTEGRINS
Leukocyte homing
&
Cell activation
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9. Adhesion molecules stabilize cell-cell interactions
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10. Priming Co-stimulation
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11. Co-stimulation
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12. Co-stimulation
Fig 8.12
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13. Improper Co-stimulation
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14. Activation only by professional APC
Activated
Anergy
Fig 8.13
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15. Maturation of Dendritic cells
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Fig 8.14

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19. B cell Ag presentation
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22. 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
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23. Co-stimulation leads to IL-2 expression
Low affinity
IL-2 receptor
IL-2
High affinity
IL-2 receptor
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24. 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
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25. Cell-surface Molecule expression changes with activation of T cell
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