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Major Histocompatability Complexes (view source)
Revision as of 10:29, 16 May 2012
, 10:29, 16 May 2012no edit summary
==MHC I==
==MHC I==
===Structure===
===Structure===
[[Image:MHC I Structure.jpg|thumb|right|200px| Structure of MHC I molecule - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]
MHC class I is expressed on virtually all nucleated cells and consists of a membrane-associated heavy chain bound non-covalently with a secreted light chain. The heavy chain is made up of three distinct extracellular protein domains - α1, α2 and α3. The heavy chain C - terminus is cytoplasmic.
MHC class I is expressed on virtually all nucleated cells and consists of a membrane-associated heavy chain bound non-covalently with a secreted light chain. The heavy chain is made up of three distinct extracellular protein domains - α1, α2 and α3. The heavy chain C - terminus is cytoplasmic.
The light chain is known as β2-microglobulin and is similar in structure to one of the heavy chain domains. It is not membrane associated but binds to the α3-domain of the heavy chain. [[Image:MHC I Structure.jpg|thumb|left|200px| Structure of MHC I molecule - Copyright Prof Dirk Werling DrMedVet PhD MRCVS]]
The light chain is known as β2-microglobulin and is similar in structure to one of the heavy chain domains. It is not membrane associated but binds to the α3-domain of the heavy chain.
The MHC class I domains are structurally and genetically related to immunoglobulin and TcR domains; the outer domains (α1 and α2) are like the variable domains and the α3 domain and β2m are like the constant domains.
The MHC class I domains are structurally and genetically related to immunoglobulin and TcR domains; the outer domains (α1 and α2) are like the variable domains and the α3 domain and β2m are like the constant domains.
===Presentation Pathway===
===Presentation Pathway===
[[Image:MHC I processing.jpg|thumb|200px|left|'''MHC I presentation pathway, courtesy of B. Catchpole, 2008''']]
MHC I presents '''endogenous''' (intracellular) peptides. Viral proteins are broken down to peptides by the proteasome and transferred to the endoplasmic reticulum (ER) via transporters associated with antigen processing (TAP) molecules. In the ER peptides are processed with empty MHC I molecules and exported to the cell surface for presentation to the T-cell receptors of [[T_cells#Cytotoxic_CD8.2B|CD8<sup>+</sup> T-cells]]
MHC I presents '''endogenous''' (intracellular) peptides. Viral proteins are broken down to peptides by the proteasome and transferred to the endoplasmic reticulum (ER) via transporters associated with antigen processing (TAP) molecules. In the ER peptides are processed with empty MHC I molecules and exported to the cell surface for presentation to the T-cell receptors of [[T_cells#Cytotoxic_CD8.2B|CD8<sup>+</sup> T-cells]]