Immunogenicity of virus-induced rat osteosarcoma.

The immunogenicity of a virus-induced rat osteosarcoma was studied utilizing the lymphocyte microcytotoxicity test. Intratibial injection of murine sarcoma virus (Moloney) resulted in the development of palpable tumors at the injection site which on histopathological examination appeared to be osteosarcomas. In 73 per cent of animals injected these tumors progressed and metastasized to the lungs. Lymphocytes from these "progressor" animals demonstrated an ability to kill osteosarcoma cells in vitro (as quantitated in the microcytotoxicity test) while serum from these animals abrogated or blocked the cell-mediated cytotoxicity. In the remaining animals the tumors either failed to develop or regressed spontaneously. Lymphocytes from these "regressor" animals also demonstrated cytolytic activity against osteosarcoma cells in vitro, but serum failed to block the lymphocyte-mediated cytolysis. Both regressor and progressor groups demonstrated humoral cytotoxic antibodies to tumor antigen on the basis of the ability of their serum to kill tumor cells in vitro.