Common Transplantation Antigens on Methylcholanthrene-induced Murine Sarcomas Detected by Three Assays of Tumor Rejection

The belief persists that chemically induced sarcomas carry individually specific transplantation antigens that do not confer cross-immunity against cell challenge with other chemically induced tumors even when induced by the same carcinogen. Cross-reacting antibody-binding determinants have been reported to exist on such tumors but not on transplantation antigens when the tumors are used as immunogens to elicit an immune response in syngeneic recipients. We deliberately selected two such model tumors as examples for study. These tumors were well documented in the literature to carry only individually specific antigens. Substantial cross-reaction was readily demonstrated in BALB/c mice between these two 3-methylcholanthrene-in-duced sarcomas, which were previously reported to display only individually unique transplantation antigens. The observed cross-reaction between the 3-methylcholanthrene sarcoma lines was shown to be dependent upon the method of prior immunization used as well as the dose of the secondary challenge. Specificity between the surface antigens on the 1315 and 1321 sarcomas was obtained only in experiments in which initial immunization was achieved by excision of progressively growing tumors followed by rechallenge with either the homologous or reciprocal tumor line. In such experiments, cross-protection was reproducibly obtained at low doses of secondary challenge cells (1 x 10⁴), whereas specificity was observed at high secondary challenge levels (5 x 10⁵). In a series of transplantation studies, mice were preimmunized with serial doses of irradiated tumor cells and then challenged with live tumor cells. In all cases in which this regimen was used, significant (70 to 100%) cross-protection between the 2 sarcoma lines was observed. The cross-reaction appeared to be specific for the chemically induced tumors, inasmuch as preimmunization to either the 1315 or 1321 sarcoma gave no significant protection against challenge with a syngeneic tumor line of SV40-induced sarcoma cells. Cross-protection was also confirmed when different sublines of high and low in vivo passages were compared. The results obtained in the direct challenge experiments were confirmed by passive transfer of live tumor cell challenges mixed with peritoneal exudate cells from immunized animals to syngeneic, unimmunized recipients.