Eosinophil-mediated killing of schistosomula of Schistosoma mansoni: oxidative requirement for enhancement by eosinophil colony stimulating factor (CSF-alpha) and supernatants with eosinophil cytotoxicity enhancing activity (E-CEA).

Factors which enhance eosinophil-mediated killing of antibody-coated schistosomula of Schistosoma mansoni include semipurified eosinophil colony stimulating factor (CSF-alpha) and eosinophil cytotoxicity enhancing activity (E-CEA) present in supernatants from cultured mononuclear cells. We have examined the mechanism of enhancement. Both actions require oxygen in order to enhance killing and do not enhance killing under anaerobic conditions (P less than or equal to 0.005). E-CEA had no detectable effect upon oxidative metabolism. In contrast to CSF-alpha which, in our previous studies, increased superoxide anion productions and quantitative leukocyte iodination, E-CEA had no detectable effect upon oxidative metabolism. In order to test whether active oxygen products might mediate enhancement of killing, the effects of the addition of superoxide dismutase and catalase were tested. Neither enzyme showed inhibition of CSF-alpha or E-CEA enhancement of eosinophil-mediated killing. The effects of CSF-alpha and E-CEA were not additive. These studies suggest that both CSF-alpha and E-CEA exert enhancement of killing by means of an as yet unidentified oxygen requiring process.