In vitro and in vivo antitumor activity of lymphokine-induced cytotoxic cells

The present study demonstrates that LICC possess both in vitro and in vivo antitumor activity. The LICC were generated by culturing normal spleen cells with syngeneic peritoneal cells and indomethacin, or with a conditioned medium containing IL 2 with or without a putative new lymphokine, the CCDF. The LICC thus generated selectively killed the lymphoid or solid tumor targets of different H-2 haplotypes and of different etiological origins. The precursors of LICC were probably NK-like cells. The effectors were neither classical NK nor classical cytotoxic T lymphocytes. The LICC were very effective in preventing growth of both lymphoid and solid tumors in vivo, and Thy I+ cells were essential for the anti-tumor effect. The ability to generate LICC was preserved in the tumor-bearing hosts until the terminal stage of tumor growth, when the generation of suppressor T-cells interfered with LICC induction. LICC seem to play an important role in defense against non-immunogenic tumors.