Activity of rat peritoneal eosinophils following induction by different methods

The numbers and proportions of eosinophils in peritoneal washings taken from rats were increased by giving one or three injections of Sephadex G200 intravenously or physiological saline intraperitoneally or by infection with Mesocestoides corti. Purified eosinophils were morphologically similar and contained similar levels of lactate dehydrogenase and peroxidase. They were equally efficient at releasing peroxidase when stimulated with complement-coated particles. Eosinophils from infected rats and from animals given repeated injections of Sephadex showed enhanced chemiluminescent and cytotoxic responses to phorbol myristate acetate compared with cells obtained from rats given a single injection of Sephadex or saline. Sephadex-induced cells displayed more activity in antibody-dependent cell cytotoxic assays and formed a greater proportion of rosettes with antibody-treated sheep erythrocytes than did eosinophils from saline-treated or M. corti-infected rats. Only eosinophils from parasitized rats were stimulated with f-Met-Leu-Phe to lyse chick red blood cells. It is concluded that the method used to recruit eosinophils in the rat can have a marked effect on their responses in vitro and this needs to be considered in studies of functional activity.