Membrane molecules of murine and human origin are isolated and characterized with emphasis on molecules involved in the immune response. The goal of these studies is to gain an understanding of their function in molecular terms as well as to gain knowledge of their evolutionary relationships. Project areas include: (1)studies on murine H-2 and I a major histocompatibility complex antigens, (2)structural studies on human HLA-variant molecules and (3)Preliminary structural studies on other murine (Ly6.2) and human lymphocyte antigens (OKT3 series). Studies on H-2 antigens have resulted in the extensive sequence information for H-2Kb, Kd, Dband Dd. These data revealed areas of polymorphism, sites glycosylation, location of disulfide bridges and variation in chain length as well as other interesting characteristics of these molecules. Studies on Ia are seeking to prove whether or not two structurally distinct IE molecules are present in the mouse.