Expression of high-affinity IgE receptors (FcεRI) on peripheral blood basophils, monocytes, and eosinophils in atopic and nonatopic subjects: Relationship to total serum IgE concentrations

Background: High-affinity IgE receptors (FcεRI) have been identified on peripheral blood basophils, monocytes, and eosinophils; but the relative receptor expression on these cells and their relationship to atopy are unclear. Objective: The aim of this study was to compare FcεRI expression on these cell types and assess their relationship to total serum IgE concentrations in subjects with atopic asthma, rhinitis, or dermatitis compared with nonatopic control subjects. Methods: Flow cytometry was used to evaluate FcεRI expression by determining the specific mean fluorescence of the binding of two anti-FcεRI α-chain monoclonal antibodies (15-1, which competes with IgE for receptor binding, and 22E7, which is noncompetitive). Results: Compared with basophils FcεRI expression (determined by 22E7 specific mean fluorescence) was greatly reduced on monocytes and was only detectable on eosinophils in a small minority of subjects. Nevertheless, FcεRI expression on all three cell types was significantly increased in atopic patients compared with nonatopic control subjects (p < 0.0001 for basophils, p = 0.003 for monocytes, and p = 0.039 for eosinophils). FcεRI expression on both basophils and monocytes in all subjects correlated significantly with serum IgE concentrations (r = 0.86 and 0.55, respectively; p < 0.001). For each subject, and on all three cell types, the specific mean fluorescence after 22E7 staining was greater than with 15-1, implying some degree of receptor occupancy. Conclusion: FcεRI expression on peripheral blood monocytes was considerably less than on basophils and barely detectable on eosinophils. Elevated FcεRI expression was observed in atopic subjects with all three cell types, suggesting a role for these receptors in IgE- mediated allergic inflammation. The possibility of common regulatory mechanisms was suggested by the correlation of FcεRI expression on basophils and monocytes with serum IgE concentrations.