Major Histocompatibility Complex Class I A (MHCA)

HLA-A is a component of certain MHC class I cell surface receptor isoforms that resides on the surface of all nucleated cells and platelets. The receptor is a heterodimer, and is composed of a heavy, α chain, and smaller beta (β) chain. The alpha chain is encoded by a variant HLA-A gene and the beta chain (β2-microglobulin) is composed by the invariant Beta-2 microglobulin gene.
For humans, as in most mammalian populations, MHC Class I molecules are extremely variable in their primary structure, and HLA-A is ranked among the genes in humans with the fastest evolving coding sequence. After typing millions of individuals, hundreds of variant alleles and isoforms have been identified.