In vivo transfer of antitumor activity by peritoneal exudate cells from mice treated with C. parvum

We have investigated whether peritoneal exudate cells (PEC) from C. parvum (CP) treated (C3Hf/Bu mice could transfer in vivo the resistance against a syngeneic fibrosarcoma (FSa). Inhibition of tumour development and prolongation of survival of recipients were observed when CP-activated PEC were admixed with FSa cells before their intraperitoneal (ip) or subcutaneous (sc) injections into normal mice. The antitumour activity increased with the increase of the ratio of effector to target cells. Heat killed CP-PEC were unable to transfer the resistance. Also, pretreatment of recipients with 600 rads whole body irradiation (WBI) substantially reduced the efficacy of CP-PEC. Reconstitution of WBI mice with mixed normal spleen and lymph node cells, or spleen cells alone, or bone marrow cells did not restore the antitumor activity of transferred CP-PEC. In fact, reconstituted mice showed a further reduction of transferred antitumor resistance. CP-PEC activity was also inhibited in sc transfer experiments when normal PEC, spleen cells, T-cells or even fetal fibroblasts were admixed with tumor cells and CP-PEC. Possible reasons for the failure of WBI recipients to be fully protected by transferred CP-PEC are discussed.