Abstract
Attempts were made to induce immunity to 5 spontaneous rat sarcomas transplanted into syngeneic recipients. Rats were immunized by surgical removal of growing tumour transplants or by treatment with attenuated tumour, followed by challenge with tumour cells in suspension. Two tumours wee apparently not immunogenic, but a low level of immunity was induced against 2, and weak evidence of immunity was observed with another. Induced immunity was individually specific rather than cross-reactive. It is concluded that, contrary to some reports, some spontaneous animal tumours are immunogenic in the strain of origin.