In vitro demonstration of cryosurgical augmentation of tumor immunity.

C57B1 mice bearing methylcholanthrene-induced fibrosarcomas (MCA-10) and receiving a single cryosurgical treatment to those tumors showed significantly greater humoral and lymphocyte-mediated cytotoxicity to MCA-10 target cells than did untreated tumor-bearing animals or mice which had undergone tumor amputation. Sera and lymphocytes from normal animals receiving crycosurgery demonstrated no immunity to the MCA-10 target cells. Specific immunity to the MCA-10 line following tumor cryosurgery was demonstrated since lymphocytes and sera from cryosurgically treated tumor-bearing mice were not cytotoxic to a different methylcholanthrene-induced sarcoma (MCAP) in C57 mice or a malignant melanoma (S91) being transferred in Balb/C mice. It can be concluded that cryosurgical treatment of the MCA-10 sarcoma does not produce heightened immunity to H-2 transplantation antigens, nor does it nonspecifically stimulate the immune system. Instead, the result of tumor cryosurgery appears to be a boosting of the immune response to the tumor-specific antigens of the sarcoma.