Regulation of human granulocyte function by products derived from murine tumors

Murine EL-4 thymoma was found to produce a factor that activated antibody-dependent cell-mediated cytotoxicity by human eosinophils and neutrophils. The eosinophil-activating factor had some properties similar to human eosinophil colony-stimulating factor in being heat stable, inactivated by 2-mercaptoethanol, and cochromatographing by gel filtration with a factor that promoted the growth of pure eosinophil colonies from human bone marrow. The neutrophil-activating factor from EL-4 was also heat stable but was not inactivated by 2-mercaptoethanol and was found in two peaks on chromatography, neither having human neutrophil-CSF activity but one cochromatographing with mouse granulocyte-macrophage CSF. EL-4 therefore secretes factors that activate two types of human granulocytes. Several other murine thymomas and macrophage cell lines produced a neutrophil-activating factor, the production of which could not be correlated with that of several other known lymphokines. Murine tumors produce factors that activate human granulocytes.