Q: What is MHC? A: major histocompatiability complex Q: What is a syngeneic graft? A: graft b/w genetically identical animals Q: What is the human equivalent to a syngeneic graft? A: autologous graft Q: What is an allogeneic graft? A: graft b/w individuals with dissimilar genetics Q: How do human transplants (allogeneic) work? A: the immune response must be suppressed Q: What is a graft vs. host disease? A: the graft attacks the host, usually marrow Q: What are the 2 classes of genes involved in graft rejection? A: MHC Class I and MHC Class II Q: What are MHC Class I proteins in humans? A: HLA antigens ( human leukocyte antigens) Q: What are MHC Class II proteins in humans? A: DR, DQ, DP Q: Where are the MHC gene products found? A: On cell surfaces Q: Are MHC gene products secreted? A: No, they are cell surface receptors Q: What are the MHC Class I gene products (3)? A: HLA-A, HLA-B, HLA-C Q: What is beta2 microglobulin A: A protein that forms a heterodimer with class I protein Q: How many different Class I chains do humans have on each cell? A: 6, due to co-dominant expression, A=B=C Q: List the MHC Class I protein domains (5) A: Extracellular (3), alpha 1, 2 & 3, transmembrane, cytoplasmic Q: What domains houses the cleft? A: the extracellular domains Q: How long is the peptide that fits in the Class I cleft? A: approximately 9 amino acids Q: What domains are polymorphic on MHC I? A: alpha 1 and alpha 2 Q: Why is the alpha 3 domain constant, on MHC I? A: so beta2 microglobulin can attach, as well as CD8 binding Q: Can we ever see the MHC I cleft empty? A: No, either self, virus or degraded Q: What domain is polymorphic on MHC II? A: alpha 1 and beta 1 Q: What domains are constant on MHC II? A: alpha 2 and beta 2 Q: Where do the peptides for a Class I protein come from? A: self or viral proteins synthesized in the cell Q: Class II proteins present peptides from? A: extracellular entities Q: Enzymes that create peptides presented on the MHC II are? A: endosomal/lysosomal proteases Q: Enzymes that create peptides presented on MHC I are? A: cytosolic proteasomes Q: What is the site of peptide loading in the MHC II? A: specialized vesicular compartments Q: What is the site of peptide loading in the MHC I? A: endoplasmic reticulum (ER) Q: What is TAP? A: tranporter associated with antigen presentation, class I Q: Which way does TAP transport peptides? A: cytosol to inside the ER, backwards Q: What happens if an MHC doesn't have a peptide in the cleft? A: it is degraded Q: Where does CD4 bind to MHC II? A: beta 2 domain Q: What is a CLIP? A: self peptide that is removed from MHC II so it can bind foreign peptides Q: What are TAP 1 & 2? A: peptide transporters in the ER, for MHC I Q: What is co-dominant expression? A: both parental alleles of each MHC gene are expressed Q: What does co-dominant expression do? A: increase the number of different MHC molecules that can present peptides to T cells Q: Why are polymorphic genes good? A: they increase the number of alleles in a poplulation Q: What does the increased number of alleles in a population do? A: allows for different individuals to respond to different microbes, ensures survival of species Q: Where are MHC IIs found (3)? A: Professional AP; dendritic cells, B cells, and macrophages Q: Where are MHC Is found? A: All cells Q: What do CD8, CTLs do? A: kill any virus infected cell Q: What do CD4 cells do? A: helper cells, activate antibody response Q: What recognizes MHC chains? A: T cell receptors (TCR) Q: What 2 things must the TCR see and bind? A: class I chain and the peptide Q: What effector cell recognizes MHC I proteins? A: CD8 T cells, cytotoxic Q: What cells express MHC I chains? A: all cells Q: How many amino acids can fit in a MHC II cleft? A: 9 to 15 amino acids Q: What cells express MHC II chains (3)? A: B cells, macrophages, dendritic cells Q: What are APCs? A: antigen presenting cells Q: What TCR recognizes MHC II chains? A: CD4 T cells Q: What do CD4 T cells do? A: increase antibody response