ENHANCEMENT OF BACTERIAL UPTAKE AND KILLING IN LYMPHOKINE‐ACTIVATED HUMAN MONOCYTES

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Abstract
Whether lymphokines affect bacteria in a direct and/or an indirect fashion via monocytes was studied. Lymphokine-rich supernatants were generated by stimulating mononuclear cells with killed Bacillus subtilis. Various strains of bacteria were incubated in these culture supernatants and plated. Also, monocytes were incubated in the supernatants, after which their capacity to phagocytose and kill Staphylococcus aureus was measured. The culture supernatants evidently did not contain activities exerting a direct effect on bacteria. They did, however, contain factors activating monocytes. The uptake and the killing of staphylococci increased 91% and 68%, respectively, after 3 days'' incubation in lymphokine-rich supernatants. The monocyte-activating principle eluted in Sephadex G-100 chromatography over a wide MW range (> 68,000 to < 23,000), was not inactivated at 56.degree. C and was reduced by L-fucose. It thus shared the characteristics of human MIF [macrophage inhibiting factor] or MAF [macrophage activating factor].