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18 Cards in this Set
- Front
- Back
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Describe class 1 MHC genes.
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encode glycoproteins found on the surface of all nucleated cells
presents Ags to CD8/cytotoxic T cells |
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Describe class II MHC genes.
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Encodes glycoproteins on APCs
presents processed Ag to CD4/T helper cells |
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Describe class III MHC genes.
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encode various secreted proteins that have immune functions
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How are class I MHC molecules organized?
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into A, B, and C regions
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How are class II MHC molecules organized?
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DP, DQ, DR arranged in pairs endcoding alpha and beta chains
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MHC is a collection of genes on which chromosome?
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chromosome 6
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The set of MHC genes inherited from each parent is called what?
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haplotype
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Compare the structure of Class I and Class II molecules.
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Class I - alpha chain with 3 domains, beta-2 microglobulin; deep socket
Class II - two nonidentical chains, 2 alpha and 2 beta domains; open pocket |
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Each individual can only express how many different class I molecules and class II molecules?
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class I - 6 different molecules
class II - 12 different molecules |
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The highest levels of MHC I are found on what and the lowest levels are found on what?
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highest - lymphocytes
lowest - neural cells (fibroblasts, muscle cells, hepatocytes also express low levels) |
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What are TAP proteins required for?
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loading of peptides (processed Ags) into the cleft of MHC molecules
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What does a RR = 1 mean?
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optimal - HLA expression occurs with the same frequency in the patient and general pop'n
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What is self-MHC restriction?
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CD4 and CD8 T cells can only recognize Ag when coupled with a self-MHC molecule
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What cells are considered professional APCs?
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dendritic cells, B cells, macrophages
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The cytosolic pathway processes what type of Ags and is presented by what MHC class?
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endogenous
MHC I |
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The endocytic pathway processes what type of Ags and is presented on what MHC class?
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exogenous Ag
MHC II |
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Describe MHC I peptide processing.
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1. endogenous Ag (viral or cancer protein) is degraded into a proteasome
2. the resulting peptides are transported by TAP to rough ER 3. alpha and beta-2 microglobulin are made in rough ER 4. Class I MHC alpha chain binds calnexin (chaperone), then beta-2 microglobulin. Calnexin disassociates, Calreticulin and Tapasin bind. MHC caputures peptide, chaperones disassociate 5. Class I MHC-peptide is transported from RER to golgi to plamsa membrane |
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Describe MHC II peptide processing.
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1. Class II MHC alpha and beta bind invariant chain, blocking the binding of endogenous Ag
2. MHC complex is routed through golgi to endocytic pathway compartments 3. Invariant chain is degraded, leaving CLIP fragment 4. Exogenous Ag is taken up, degraded through endosome, endolysosome, and lysosome, and routed to endocytic pathway compartments 5. HLA-DM mediates exchange of CLIP for antigenic peptide 6. Class II MHC-peptide is transported to plasma membrane |
