The long range goal of this laboratory is to determine the function of the histocompatibility-linked immune response (Ir) genes in the regulation of the immune response and in the control of immunocompetent cell interactions. At present, the research effort is divided into two main areas: 1) the role of the I-region associated (Ia) antigens and Ir gene products in macrophage-T lymphocyte interaction, T lymphocyte-B lymphocyte interaction, and T lymphocyte antigen recognition. 2) Genetic, serological and physicochemical studies of the antigens of the guinea pig major histocompatibility complex.