Biologic, functional and chemical characterization of cell surface structures of normal lymphoid and malignant cells are under investigation. Antigen (HLA) controlled by the major histocompatibility complex (MHC) have been assessed in diseased populations and at risk families. Results indicate that several interacting genes and gene orientation predispose to disease states. Immune response, specifically directed to the insulin molecules appears to be controlled by the human MHC. Immunoprecipitation analysis of antigens controlled by the MHC DR gene region suggests at least 3 gene products which are complexes of at least 3 different heavy and 6 light chains. Intact antibodies reacting with these structures suppress in vitro lymphocyte stimulation by antigen and Ig productions. Cultured lymphoma cell possessing the HTL virus express inappropriate HLA antigens. Naive fetal cells are induced to express these HLA antigens when infected with HTLV. Lymphocytes from homosexual men have altered helper/suppressor ratios with decreased total helper cells. This alteration appears associated with amyl nitrate use.