Characterization of the Individual and Cross‐reactive Antigens Involved in the Anti‐tumor Immunity Induced by Use of an H‐2K‐erbB Recombinant Gene Transfectant

The specificities of the antisera raised in the CDF4 mice that had been immunized with the Pl. HTR tumor cells xenogenized by transfection with recombinant H‐2Kb‐erbB gene were studied. The antisera cross‐reacted with a broad range of tumor cell lines maintained either in vitro or in vivo in an immunofluorescence assay. However, they did not react at all with syngeneic normal tissue cells from thynms, spleen, bone marrow and fetal liver. Even though antigens related to the murine leukemia virus and murine mammary tumor virus (MuMTV) were demonstrated in many of the tumor cell lines tested with specific antibodies, these antigens did not seem to be primarily involved in the anti‐Pl. HTR antibody activity. The 74 kDa molecule, which was precipitated by the anti‐Pl. HTR anti‐serum from the surface radiolabeled cell extract of Pl. HTR tumor and was discriminated from the 70 kDa molecule precipitated by the anti‐MuMTV serum, was widely distributed among various tumor cell lines tested, but was absent in normal tissue cells. In contrast to the extensive cross‐reaction by the antibody, the cytotoxic T lymphocyte generated in the Pl. HTR immune mice were shown to be specific to the Pl. HTR tumor, and the 98 kDa molecule was precipitated by the anti‐Pl. HTR serum from the Pl. HTR tumor but not from other tumors tested. It is suggested from these results that the 98 kDa molecule is a candidate for an individual tumor‐specific transplantation antigen, and is immunodominant for inducing cytotoxic T lymphocytes to coexisting intrinsic retroviral antigens and other serologically cross‐reactive tumor antigens.