MHC class I

Reduction in the normal levels of surface class I MHC, a mechanism employed by some viruses[4] and certain tumors to evade CTL responses, activates NK cell killing.[5] PirB is expressed in the central nervous system and diminishes ocular dominance plasticity in the developmental critical period and adulthood.[5] PirB loss of function mutant mice also exhibited enhanced plasticity after monocular deprivation during the critical period.They have membrane proximal Ig fold The peptide translocation from the cytosol into the lumen of the ER is accomplished by the transporter associated with antigen processing (TAP).Once the peptide is loaded onto the MHC class I molecule, the complex dissociates and it leaves the ER through the secretory pathway to reach the cell surface.[18] MHC class I molecules are loaded with peptides generated from the degradation of ubiquitinated cytosolic proteins in proteasomes.As viruses induce cellular expression of viral proteins, some of these products are tagged for degradation, with the resulting peptide fragments entering the endoplasmic reticulum and binding to MHC I molecules.As an evolutionary response to this method of immune surveillance, many viruses are able to down-regulate or otherwise prevent the presentation of MHC class I molecules on the cell surface.[2] Since their emergence in jawed vertebrates, this gene family has been subjected to many divergent evolutionary paths as speciation events have taken place.
Simplified diagram of cytoplasmic protein degradation by the proteasome, transport into endoplasmic reticulum by TAP complex, loading on MHC class I, and transport to the surface for presentation
Membranomemajor histocompatibility complexMHC class IIcell surfacenucleatedvertebratesplateletsred blood cellscytotoxic T cellspeptidescytosolicproteasomecross-presentationnatural killer cellsplasticitycentral nervous systemocular dominancecritical periodsynaptic plasticityvisual cortexβ2-microglobulinHLA geneBeta-2 microglobulinT-cellsT cell receptorternary complexheterodimersdisulfide bondcytosolproteolyticendoplasmic reticulumtransporter associated with antigen processingABC transporterPeptide loading complextapasincalreticulincalnexinsecretory pathwayposttranslational modificationsN-glycanGolgi apparatusalbuminubiquitinatedproteasomesapoptosiscell-mediated immunitynatural killerrecent common ancestorjawed vertebratesspeciationpolymorphismsallelebalancing selectionpathogensBirth-and-deathgene duplicationpseudogenizationWayback MachineBibcodeMedical Subject HeadingsTransmembrane receptorsimmunoglobulin superfamilyimmune receptorsFc receptorFcεRIFcεRIIC-type lectinFcγRIFcγRIIFcγRIIINeonatalFcαRIFcα/μRPolymeric immunoglobulin receptorB cellsCo-receptorT cellsLigandsCo-receptorsCytokine receptorKiller-cell IG-like receptorsKIR2DL1KIR2DL3KIR2DL4KIR2DS1KIR2DS4KIR3DL1KIR3DL2KIR3DL3Leukocyte IG-like receptorsLILRA1LILRA2LILRA3LILRA4LILRA5LILRB1LILRB2LILRB3LILRB4LILRB5HLA-DMHLA-DOHLA-DPHLA-DQHLA-DRHuman leukocyte antigenMinor histocompatibility antigenBlood transfusionArrestinCalgranulinHuman blood group systemsCell adhesion moleculesCluster of differentiation