Studies on the antigenicity of radiation-induced murine osteosarcomata.

The immunogenicities of 15 murine osteosarcomata induced with a bone seeking radioisotope ((90)Sr) in normal and chimaeric CBA mice were studied. Attempts were made to induce tumour-specific immunity in syngeneic mice by treatment with x-irradiated (15,000 rad) tumour or surgical excision of developing subcutaneous tumour grafts. Resistance was evoked against 6 tumours and this was relatively weak. With the remaining tumours, no resistance against the immunizing tumour could be demonstrated, even though the transplantation tests were made highly sensitive by the use of inocula of as few as 2 × 10(3) cells in pre-irradiated (400 rad) hosts. Sera from mice immunized against each of the tumours were tested against viable cells of the immunizing tumour by indirect immunofluorescence. In no instance did tumour antisera give a convincing reaction with tumour cells although alloantisera raised by hyperimmunization of H-2 identical and H-2 different donors with osteosarcomata consistently gave strongly positive reactions. The results are interpreted as illustrating the weak tumour specific antigenicity of radiation-induced murine osteosarcomata. The possibility that antigenic deficiency is a consequence of immunosurveillance in this tumour system is discussed.