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 anti-FcalphaR antibodies, were found to be differentially expressed on eosinophils and neutrophils. Neutrophils were the major granulocyte population expressing FcalphaR, and they expressed much higher levels of FcalphaR than eosinophils. The expression of FcalphaR by eosinophils could be upregulated approximately threefold by Ca2+ ionophore treatment in a dose- and time-dependent manner. This effect, which was blocked by a chelating agent, was not duplicated by other cellular stimuli. Eosinophils in allergic individuals displayed enhanced FcalphaR expression, whereas neutrophils did not. The FcalphaR on eosinophils had a higher 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 for both cell types. The data indicate that expression of FcalphaR molecules with a characteristic glycosylation pattern is upregulated on eosinophils in allergic individuals.