Biochemical Diversity of the Human MHC Class II Antigens

The diversity of the human MHC class II anti gens expressed as functionnal structures at the surface of immunocompetent cells arose through a multistep procedure of biochemical modifications, each contributing to the final complexity of the system. A precise knowledge of the structural diversity of the human Ia antigens at the protein level is thus required in order to better understand the mechanisms underlying the function of MHC class II antigens in regulating the immune responses. I will review recent data from our Laboratory which adress the different levels of structural polymorphism and emphasize some of the post translational modifications which may be important in evaluating the structure-function relationships in the human Ia system.