The MHC and MHC molecules 2

Published on May 8, 2022   51 min

Other Talks in the Series: The Immune System - Key Concepts and Questions

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Hello, this is Jim Kaufman from the University of Edinburgh and the University of Cambridge with the second of two lectures on the MHC and MHC molecules.
In our last talk, we defined MHC molecules and discussed their central role. We considered the classical class I and class II MHC molecules and the non-classical MHC molecules in some detail and we finished with the organisation of MHC genes in the MHC of humans and mice. In the second talk, we're going to consider more closely genetics, nomenclature, polymorphism and function. Then ask the question what drives the high polymorphism of classical MHC molecules?
Last time we finished with this picture of the human and mouse MHCs, which are extremely complex with hundreds of genes, including those encoding the classical and non-classical MHC molecules. Let's discuss the nomenclature, particularly of the classical MHC molecules.
How are these genes named? Starting with the classical class I genes. For humans, these genes are called HLA -A, B, and C. For mouse H-2K, D, and in some haplotypes, L. As we mentioned last time, these genes are due to different expansions. HLA-A, B, and C genes are more closely related to each other than they are to any of the mouse genes. For the classical class II genes, there's HLA-DRA and DRB for the DR α and β gene, and likewise DQA and DQB and DPA and DPB. In mouse, there's H2Eα and Eβ. But unlike class I genes, these are direct orthologs of the human DRA and DRB. Similarly, H-2Aα and H-2Aβ are orthologs of DQA and DQB. But there are no mouse orthologs of DPA and DPB. However, there is a second DRB locus in most human haplotypes. The major one is always called DRB1; the others have names like DRB3, DRB5, etc.