The rauscher-MuLV-induced leukemia, RBL-5, bears two tumor-associated transplantation antigens expressed on distinct molecules

Tumor cells frequently express on their surface a new antigenic determinant which renders them immunogenic in the host animal. When immunity to this antigen results in rejection of a syngeneic tumor transplant, it is referred to as a tumor-associated transplantation antigen (TATA). RBL-5 is a Rauscher murine leukemia virus (MuLV}-induced leukemia of C57BI/6 origin that is potently immunogenic and shares a TATA with other tumors induced by the closely related Friend and Moloney-MuLVs (FMR-TATA). We have recently isolated a 175 kilodalton (kd) glycoprotein (gp175) which has all the properties expected of the FMR-TATA (Rogers et al., 1984). When this molecule was separated from a purified total glycoprotein fraction by DEAE chromatography, the remaining glycoproteins still contained a highly immunogenic TATA. Control experiments involving radioimmunoassay and immunoprecipitation with rabbit anti-gp 175 indicated that this immunogenicity was not due to residual gp 175 or breakdown products of gp 175. We therefore conclude that RBL-5 expresses at least two distinct TATAs: gp175 and another glycoprotein distinguished from gp 175 by its elution from a diethylaminoethylcellulose (DE52) column. These results, from a completely in vivo system, support data with other tumors obtained by in vitro methods and indicate that tumor cells may express several immunogenic molecules.