IMMUNOLOGICAL ANALYSIS OF ENHANCED SPONTANEOUS METASTASIS IN WKA RATSFOLLOWING CRYOSURGERY

We have previously reported that inhibition of anti-tumor immune respo nses and enhancement of metastatic tumor growth occurred in rats follo wing cryosurgery of the transplantable 3-methlcholanthrene-induced rat fibrosarcoma KMT-17. In this study, to elucidate the immunological re sponses in rats following cryosurgery, we examined whether rat serum o btained from rats which underwent cryosurgery (c-serum) might affect t he in vivo neutralizing activity of the Winn assay. In this assay, c-s erum did not reduce the anti-tumor immunity, though spleen cells obtai ned from rats undergoing surgical excision indicated strong anti-tumor immunity as compared with cryosurgery. Thus, we examined the anti-tum or responses of spleen cells. Macrophages were obtained from the glass adherent fraction of rat spleen cells following cryosurgery and these macrophages were used for cytostatic activity against KMT-17 cells. C ytostatic activity was not reduced by cryosurgery The spleen cells obt ained from rats receiving cryosurgery were intravenously transferred i nto other rats that were previously immunized with 80 Gy-irradiated KM T-17 cells, end an alteration of tumor growth modulated by this adopti ve cell transfusion was observed. The anti-tumor resistance of rats wa s diminished by the adoptive transfusion of spleen cells treated with cryosurgery, though this diminution disappeared following anti-T serum and immune complement treatment of spleen cells. These results sugges t that immune-suppression following cryosurgery may be mainly caused b y suppressor T cells.