Participation of polymorphonuclear leukocyte-derived factor in murine tumour cell killing

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Abstract
Previous studies showed that murine polymorphonuclear leukocytes (PMNs) lyze tumour cells in the presence of wheat germ agglutinin or actinomycin D. This paper reports studies on whether a soluble factor participates in PMN-mediated cytolysis dependent on lectin or a chemotherapeutic drug. Tumour lysis was observed with supernatants from PMN cocultured with wheat germ agglutinin or actinomycin D. The supernatant from cultures of PMNs alone was not cytotoxic, but addition of these agents to the supernatant induced tumour lysis. PMNs released a soluble factor spontaneously into the medium and cytolysis was induced by a combination of this factor and wheat germ agglutinin or actinomycin D. This factor was not an oxygen metabolite, but a protein with a molecular weight of approximately 100 K daltons. These results suggest that a soluble factor(s) from PMNs participates in tumour killing in cooperation with appropriate reagents.