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11 Cards in this Set
- Front
- Back
exogenous Ag
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exogenous Ag:
- MHC II process this phagocytized material and present its Ag to Th cells - Th cells can only recognize foreign Ag if bound to an MHC II on an APC |
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exogenous Ag processing
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exogenous Ag processing:
1. foreign material phagocytized and taken into phagosome 2. phagosome fuses with lysosomes= endosome 3. inside endosome: proteins broken down into peptide fragments 4. endosome fuses with other endosomes carrying newly synthesized MHC II |
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exogenous Ag presentation
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exogenous Ag presentation:
1. MHC II loaded with peptide (12-24 aa long) fragment and transported to the cell surface - MHC II specifically bind only some peptides created in processing= select epitopes presented to T cells - APC can express about 200K different MHC II so can present many Ag silmultaneously |
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endogenous Ag
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endogenous Ag:
- mediated by MHC I - present Ag originating from body's own cells ( NOT phagocytized): foreign proteins are in cytoplasm not the phagosome - eg proteins made by virus-infected cells |
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endogenous Ag processing
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endogenous Ag processing:
1. infected cell chops up microbial proteins into fragments 2. fragments 9 aa long (only!!) bind to MHC I |
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endogenous Ag presentation
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endogenous Ag presentation:
1. protein fragments bound to MHC I are carried to the cell surface 2. CTLs respond to Ag stimulation by destroying infected cells - not only includes microbial infection, but neoplastic cells |
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APCs and MHC
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APCs are:
- nucleated: can make and express both MHC I and II - able to present both exogenous and endogenous Ag at the same time - MHC I: becomes infected - MHC II: engulf and present foreign material |
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Cross-presentation/ priming
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cross-presentation/ priming:
- not fully understood - under some circumstances, exogenous Ag may enter the endogenous Ag pathway and be presented by MHC I to CTLs |
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example of cross-priming
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cross- priming:
- macrophage or dendritic cell endocytoses viral Ag (eg killed virion) which are transported from the phagosomes into the cytoplasm - enters endogenous Ag pathway: CTL response - important in viral immunity |
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heat shock proteins gen
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heat shock proteins:
- induced in cells by stress: change in T, stavation, toxins - in all organisms at low levels - molecular chaperones of proteins through the cell |
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heat shock proteins fx
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heat shock proteins:
1. binds endocytozed viral (exogenous) Ag and channels into endogenous pathway - eg killed virus vaccines shuttled into endogenous pathway to be presented by MHC I to CTLs 2. likewise, tumor Ag from exogenous to endogenous pathway - important as these Ag can then stimulate a CTL and Th cell response |