The effects of eosinophil activating factor on IgG-dependent sulphidopeptide leukotriene generation by human...

Eosinophil activating factor (EAF) is a 40 kD protein released from cultured, unstimulated human monocytes which enhances the IgG-dependent eosinophil-mediated cytotoxicity of helminthic larvae. We have recently shown that eosinophils elaborate substantial quantities of leukotriene C4 (LTC4) during incubation with IgG-coated particles and now report that EAF, partially purified by sequential chromatography on Sephacryl S-200 and DEAE-cellulose, enhanced this IgG-dependent LTC4 production by human eosinophils in a dose- and time-dependent fashion. LTC4 production by normal density eosinophils, separated on discontinuous metrizamide gradients, was significantly increased after incubation with several dilutions of EAF (P less than 0.05), although an increase was not seen with low density cells. The enhancement was similar in degree to that seen when normal density eosinophils were activated with the bacterial analogue, f-met-leu-phe (fMLP). EAF produced a time-dependent increase in LTC4 which was significantly greater (P less than 0.01) than the control. Sulphidopeptide leukotriene (LT) generation was validated by reverse phase high pressure liquid chromatography (RP-HPLC). These results indicate that there is a firm association between monocytes, eosinophils and LTC4; an observation which may be of relevance to mechanisms in chronic asthma and related disorders, and in immune reactions against migrating helminthic larvae.