The purpose of this work is to examine the biological and chemical properties of histocompatibility antigens (H-2), tumor associated transplantation antigens (TATA) and other tumor associated proteins with the aim of determining their potential roles in tumorigenesis and the antitumor immune response. The approach is to purify the molecules by conventional biochemical techniques and/or prepare polyclonal and monoclonal antibodies against them. The purified molecules and antibodies are then used to study the biological and chemical properties of these molecules including 1) their ability to specifically influence antitumor immunity both in vivo and in vitro, 2) their subcellular distribution, association with the plasma membrane, and post-translational modification 3) their tissue distribtuion, 4) their distribution in neoplastic and preneoplastic tissue. Ultimately suitable DNA probes will be prepared and used to study the organization and expression of the genes encoding these molecules.