Tumor inhibition by effector cells cultured from progressing sarcomas

The effect of cytotoxic lymphoid cells emerging in primary cultures of an antigenic sarcoma of strain 13 guinea pigs was investigated on tumor growth in vivo. The growth of lethal tumor inocula was inhibited or the tumor cells were completely rejected in normal syngeneic recipients treated s.c. with low doses (5 X 10(5)) of effector cells which were mixed with the tumor cells. A higher dose (2.5 X 10(6)) of killer cells did not affect significantly tumor growth in normal recipients. Significant tumor inhibition was observed in X-irradiated recipients given high doses (2.2 X 10(6)) of effector cells locally although rejection did not occur with high frequency. Local treatment of X-irradiated recipients with low doses (5 X 10(5)) of effector cells did not influence tumor growth. Systemic treatment of normal or X-irradiated recipients with effector cells had little effect at any dose, although tumor inocula were occasionally rejected. Sonication of the cytotoxic effector cells prior to administration inhibited their tumor suppressing effect. Animals that rejected the first tumor inoculum were immune to a second lethal dose of sarcoma cells. It is indicated by the results that tumor rejection in vivo is not simply a matter of killer-target cell interaction, but rather a complex and poorly understood phenomenon.