Expression of a functional Fc epsilon RI on rat eosinophils and macrophages

Besides its crucial role in type I hypersensitivity reactions, IgE is invol ved in anti-parasite immunity. This role has been clearly demonstrated in b oth human and rat schistosomiasis, but remains controversial in the mouse, Since the cellular distribution of the high affinity IgE receptor, Fc epsil on RI, differs in humans and mice, it might explain the differences in effe ctor function of IgE between the two species, In humans, eosinophils and ma crophages induce IgE-dependent cytotoxicity toward Schistosoma mansoni larv ae, which involves Fc epsilon RI in the case of eosinophils. In the present study, we have investigated the expression and function of Fc epsilon RI i n rat eosinophils and macrophages, We demonstrate, by flow cytometry, fluor escence microscopy, and Western blot analysis, that in rats, as in humans, a functional ay, trimeric Fc epsilon RI is expressed on eosinophils and mac rophages. We also show that these two cell types can induce IgE-mediated, F c epsilon RI dependent cellular cytotoxicity toward schistosomula, These re sults thus provide a molecular basis for the differences observed between r at and mouse regarding IgE-mediated anti-parasite immunity.