Human peripheral eosinophils express functional interferon-gamma receptors (IFN-γR)

Abstract

In order to determine whether or not IFN‐γR is associated with regulatory mechanisms on human eosinophil function, we examined the expression of functional IFN‐γR on human peripheral eosinophils. In this study, peripheral blood eosinophils were obtained from seven normal controls and 12 patients (bronchial asthma, n = 9, and hypereosinophilic syndrome (HES), n = 3), and the purity of eosinophils was 97.11 ± 2. 31%, n = 19. We first showed that anti‐IFN‐γR α‐chain MoAb reacted with all tested eosinophils of both normal controls and patients by flow cytometry analysis. We also showed expression of mRNA for the α‐chain of IFN‐γR in all purified eosinophils of six individuals. Further, to characterize IFN‐γR on eosinophils, we did binding experiments with ¹²⁵I‐IFN‐γ on purified peripheral eosinophils. The linear Scatchard plot indicated a single type of high‐affinity binding sites (dissociation constant (Kd) = 3.89–4.95 × 10⁻¹⁰ M, numbers of binding sites = 183–233/cell, n = 3). To determine whether IFN‐γR on eosinophils is functional, we examined surface eosinophilic cationic protein (ECP) and CD69 induction after IFN‐γR ligation with recombinant human IFN‐γ (rhIFN‐γ) on eosinophils by flow cytometry. rhIFN‐γ stimulation significantly induced both ECP and CD69 expression on the 2–18 h‐cultured eosinophils in a dose‐dependent manner. Further, the effects of rhIFN‐γ stimulation were significantly blocked by both a neutralizing anti‐IFN‐γ MoAb and a blocking anti‐IFN‐γR MoAb. These results suggest that human peripheral eosinophils express functional IFN‐γR.