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10 Cards in this Set
- Front
- Back
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CD8+ T cells vs. NK Cells
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Both protect host from pathogen, and kill bad cells using similar cytotoxic chemicals and cytokines. They differ in that T cells have T receptors (VDJ) that recognize specific antigen and MHC abd NK cells use a variety of receptors that are encoded by allelic variation and not recombination, and can recognize absence of Class I (lack of self) an stressed cells.
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Cytotoxic T cell Balance
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Too much can cause AID, GVHD, Transplant rejection, diabetes. Too little can cause immunodeficiency like CHS and FHL.
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Cytotoxicity vs. Immune modulation
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C: granzyme, preforin, death receptor pathway
I: IFN-Y TNF. chemokines 3,4,5. IL 10 as well GM CSF |
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Death Pathway
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The T cell binds to the target cell enhaging T cell receptor and CD8 with MHC. This causes the release of preforin and grnazymes taken up by the target cell. Preforin disrupts the cell membrnae, granzyme A breaks down DNA and granzyme B activates BID which will activate apoptoisis. The T cell will also release Fas-ligand activating capsases. Fas ligand can bind Fas on the target cell or immune cell, thus terminating the immune response (fratreicide)
Another method is the TRAIL pathway which uses TNF to activate capsases. Trail from T cell binds TRAIL-R and leads to FADD binding and then capsase 8 binding. |
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Licensing
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After dendritic cells activate T cell, they must aquire the ability to prime T cells and this is done by licensing inw chi the T cell will upregulate surface CD40 which licenses the DC.
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How to hide from cytotoxic T cells?
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latency, antogenic variation, infect immune priviliged sites like the CNS, immunoevasins, produce antiapoptotic proteins, interfere with pathogen receptors.
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How do DC avoid apoptosis?
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express IAP
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NK cells surface markers
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CD56: adhesion,
CD16: FCgamma for IgG KIR: Killer Cell Ig Receptor, recgonizes MHC |
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Subsets of NK cells
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CD56 Bright/CD16 dim: release more cytokines, high proliferation, in sec. lymph. organs.
CD56dim/CD16bright: release more cytotoxins, loe proliferation, in blood |
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NK Cells Activating and Inhibitory Receptors
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Inhibitory: recognize MHC class I, ITIM, and use phospatases to inhibit apoptosis.
Activating: virus and stress proteisn, ITAL, DAP 12 adpators *most NK receptors can be expressed by an activated T cell |
