HUMAN PERIPHERAL EOSINOPHILS EXPRESS FUNCTIONAL INTERFERON-GAMMA RECEPTORS (IFN-GAMMA-R)

In order to determine whether or not IFN-gamma R is associated with re gulatory mechanisms on human eosinophil function, we examined the expr ession of functional IFN-gamma R on human peripheral eosinophils. In t his study, peripheral blood eosinophils were obtained from seven norma l controls and 12 patients (bronchial asthma, n = 9, and hypereosinoph ilic syndrome (HES), n = 3), and the purity of eosinophils was 97.11 /- 2.31%, n = 19. We first showed that anti-IFN-gamma R alpha-chain Mo Ab reacted with all tested eosinophils of both normal controls and pat ients by flow cytometry analysis. We also showed expression of mRNA fo r the alpha-chain of IFN-gamma R in all purified eosinophils of six in dividuals. Further, to characterize IFN-gamma R on eosinophils, we did binding experiments with I-125-IFN-gamma on purified peripheral eosin ophils. The linear Scatchard plot indicated a single type of high-affi nity binding sites (dissociation constant (Kd) = 3.89-4.95x10(-10) M, numbers of binding sites = 183-233/cell, n = 3). To determine whether IFN-gamma R on eosinophils is functional, we examined surface eosinoph ilic cationic protein (ECP) and CD69 induction after IFN-gamma R Ligat ion with recombinant human IFN-gamma (rhIFN-gamma) on eosinophils by f low cytometry. rhIFN-gamma stimulation significantly induced both ECP and CD69 expression on the 2-18 h-cultured eosinophils in a dose-depen dent manner. Further, the effects of rhIFN-gamma stimulation were sign ificantly blocked by both a neutralizing anti-IFN-gamma MoAb and a blo cking anti-IFN-gamma R MoAb. These results suggest that human peripher al eosinophils express functional IFN-gamma R.