An assay for macrophage activating factor based on the adherence of oil-elicited guinea pig macrophages: characterization of a lymphokine-induced release of hydrogen peroxide from elicited macrophages.

A convenient procedure is described for assaying guinea pig macrophage activating factor (MAF) in lymphokine preparations. The assay utilizes oil-elicited peritoneal macrophages from strain 2 guinea pigs and measures the capacity of macrophage cultures pretreated with lymphokine or medium to release hydrogen peroxide (H2O2) in the presence and absence of phorbol myristate acetate (PMA). The PMA-induced release measures a maintenance of macrophage adherence and activation. A novel aspect is a lymphokine-dependent release of H2O2 which occurs in the absence of PMA and which differs from the PMA triggered release. The differentiation process into lymphokine responsive cells has been studied using macrophages elicited from 2-21 days after oil injection. In addition macrophage responsiveness was examined in different strains of guinea pigs.