Immunogenicity of the Gardner lymphosarcoma for the mice of the strain C3H (H-2k). I. The effect of the 60Co-irradiation of recipients and of the interval between the immunization and transplantation of the tumor on the antitumor resistance of immunized mice.

The C3H (H-2k) mice were immunized by 60Co-irradiation-inactivated Gardner lymphosarcoma (LSG) cells. The degree of resistance of mice with transplanted tumors was determined by difference in survival curves of the immunized and nonimmunized mice. When the tumor was transplanted during 26 weeks after the last of the three immunizing injections the mean survival time of immunized mice was always prolonged over that of nonpretreated controls. The prolongation was not always significant. The slope differences between lines characterizing survival of immunized and nonimmunized groups were statistically significant when the transplantation of the tumor was performed up to the 22nd week following the immunization. A small number of immunized mice which survived 60 days without visible tumors belonged to immunized groups transplanted with the tumor up to 14 weeks after the last immunizing dose. A higher degree of resistance has been achieved in mice given increased number of immunizing injections. Similar effect was observed in mice with impaired antitumor resistance due to immunosuppressive dose of 60Co-irradiation given before the tumor transplantation. Skin grafts taken from resistant mice healed up to unaffected isologous mice as well as it was found in reciprocal transplantation experiments.