MALARIAL PARASITES AND TUMOR-CELLS ARE KILLED BY THE SAME COMPONENT OF TUMOR NECROSIS SERUM

Abstract

Tumor necrosis serum (TNS), from animals primed with macrophage activating agents and challenged with endotoxin, causes necrosis of some tumors and can kill certain tumor lines in vitro, and malarial parasites in vitro and in vivo. The possibility that the same factor is responsible for killing both tumor cells and malarial parasites was tested. In competitive inhibition experiments, parasitized [mouse] erythrocytes, but not normal erythrocytes, inhibited the cytotoxicity of TNS against a [mouse] tumor cell line. Conversely, the tumor cells inhibited the killing of Plasmodium yoelii in vitro by TNS. When rabbit TNS was fractionated by ion exchange chromatography followed by gel filtration and the fractions at each step were pooled according to their ability to kill the tumor cells, in vitro parasite killing activity correlated with tumor cell cytotoxicity to a final sample, which was purified > 600-fold. In terms of function, at least, the same component of TNS is apparently responsible for the killing of both tumor cells and malarial parasites.