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final question samples about MHC II

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Victor Barac

Major Histocompatibility Complex MHC – Collection of genes involved in immune response  Usually clustered together on a single chromosome in jawed vertebrates  jawed means they have an adaptive immune system o Humans = chromosome 6 o Mouse = chromosome 17 – Histocompatibility: when cells of one tissue can survive in the presence of cells of another tissue  MHC genes originally isolated for their role in grafts / transplants  Mismatches in MHC alleles are what cause graft rejections – MHC restriction: T cells recognize peptide antigen only when it’s bound to a self-MHC molecule MHC vs. HLA & H-2  same structure and fxn, different terminology – MHC = major histocompatibility complex  genetic complex in all vertebrates – HLA = human leukocyte antigen  name for human MHC – H-2  name for mouse MHC MHC Class III – Genes that code for associated immunological or antigen presenting molecules  Complement, interferon, tumor necrosis factor – Also contains many genes not related to immune fxn  Proteasome genes: breakdown of cytoplasmic proteins into peptides () o Recall: cylindrical garborator that destroys proteins tagged w/ ubiquitin o Has MHC class I fxn b/c it chops up big proteins into smaller useful protiens  TAP: transporter associated with Antigen Processing o Moves peptides into ER so that MHC class I molecules in ER can bind them  DMA + DMB: combine to make DM (MHC class II related molecule) o Assists class II receptor in loading peptides MHC Class I MHC Class II – Involved in response to intracellular pathogens – Class II: Involved in response to extracellular A, B, C pathogens DR, DQ, DP  Part of cellular immunity  Part of humoral immunity  Initiates CD8 (killer) T cells  Initiates CD4 (helper) T cells MHC Class I and II – Immunoglobulin superfamily members – Has multiple gene copies  lots of binding diversity  lots of immune response diversity  Co-dominantly expressed: both mom + dad MHCs are expressed on surface o Means there is a low probability for matching MHCs  Set of alleles (mom + dad) present on each chromosome o Inherit MHC as haplotype (i.e. all genes are together on one chromosome)  Both mom + dad genes are highly polymorphic (many alleles in population)  Most polymorphic nuclear encoded genes  Means there are differences at the species level, not individual level  Need polymorphism b/c there are lots of pathogens out there!  Diff alleles have diff capacities for binding peptides   # of alleles in population =  range of protection – MHC Class I and II alleles in humans  There are 3 Class I genes  we have 2 alleles o
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