HLA class I polymorphism: structure and function and still questions.

The HLA-A, HLA-B and HLA-C molecules have turned out to be highly polymorphic and functionally complex. They not only serve as peptide receptors, but also interact with beta 2-microglobulin, an alpha beta T cell receptor, CD8 and NK inhibitory molecules, all at different sites. The fact that more than 300 class I alleles have now been defined prompted us to ask the question of where polymorphism really occurs in a class I molecule.