Characterization of a cytotoxic factor induced in mouse peritoneal fluid by OK-432

A cytotoxic factor (peritoneal cytotoxic factor, PCF) was strongly induced by the injection of LPS into the peritoneal fluids of mice which had been previously primed with OK-432. In order to clarify characteristics of PCF, physicochemical and immunological studies were conducted. When incubated with LPS, the macrophages from mice primed with OK-432 induced PCF whereas the lymphocytes did not. These results indicate that PCF is different from lymphotoxin. PCF appears to be quite similar to tumor necrosis factor (TNF) in the serum for the following reasons: The two factors are similar in the mode of cytotoxic action in vitro; both factors have a tumor necrotizing effect when injected into tumor bearing mice; both are produced from macrophages; they are similar in physicochemical characteristics; and the cytotoxic activity of PCF is totally abolished by anti-TNF serum.