CHARACTERIZATION AND PURIFICATION OF A MACROPHAGE-TRIGGERING FACTOR PRODUCED IN MYCOPLASMA ARGININI-INFECTED L5178Y CELL-CULTURES

The supernatant of Mycoplasma arginini-infected murine L5178Y T lympho ma cell cultures (SN-L51) synergizes with small concentrations of IFN- gamma to activate murine peritoneal, thioglycollate-elicited macrophag es (M phi) to exhibit cytostatic activity against tumor cells. Treatme nt of M phi with IFN-gamma and SN-L51 sequentially, but not in the rev erse order, activates M phi, which indicates that SN-L51 contains a M phi-triggering factor (MTF). MTF activity could be inhibited by small concentrations of prostaglandin E(2), but not by polymyxin B. M phi ac tivated by IFN-gamma plus MTF produce cytostatic effects on tumor cell s through a nitric oxide-dependent pathway. MTF activity in SN-L51 is associated with infection of L5178Y cells by M. arginini. Mycoplasma-f ree L5178Y cells do not produce MTF activity, infection of these L5178 Y cells with M. arginini generates the activity, and supernatants of p ure M. arginini cultures contain MTF activity. MTF activity is thermos table and resistant to acid, dilute alkali, proteases, and nucleases. MTF was partially purified by ammonium sulfate precipitation, chromato graphy, electrophoresis, and electroelution. On 12.5% SDS-urea gels, M TF activity migrated with a molecular mass of 2.5 to 4 kDa. MTF activi ty and the silver staining of this band was resistant to proteinase K; however, Coomassie staining of this band was abolished by proteinase K. The combined data suggest that MTF is either a stable peptide or a peptide linked to lipid or carbohydrate.