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

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Abstract
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.