DEFINITION OF IMMUNOGLOBULIN-A RECEPTORS ON EOSINOPHILS AND THEIR ENHANCED EXPRESSION IN ALLERGIC INDIVIDUALS

Fcalpha receptors (FcalphaR), detected by the binding of IgA and by an ti-FcalphaR antibodies, were found to be differentially expressed on e osinophils and neutrophils. Neutrophils were the major granulocyte pop ulation expressing FcalphaR, and they expressed much higher levels of FcalphaR than eosinophils. The expression of FcalphaR by eosinophils c ould be upregulated approximately threefold by Ca2+ ionophore treatmen t in a dose- and time-dependent manner. This effect, which was blocked by a chelating agent, was not duplicated by other cellular stimuli. E osinophils in allergic individuals displayed enhanced FcalphaR express ion, whereas neutrophils did not. The FcalphaR on eosinophils had a hi gher molecular mass (70-100 kD) than those identified on neutrophils ( 55-75 kD). However, removal of N-linked carbohydrates from FcalphaR of eosinophils and neutrophils revealed a major protein core of 32 kD fo r both cell types. The data indicate that expression of FcalphaR molec ules with a characteristic glycosylation pattern is upregulated on eos inophils in allergic individuals.