Unique characteristics of superoxide production by human eosinophils in eosinophilic states

Abstract

Eosinophils from patients with peripheral blood eosinophilia and human neutrophils from normal subjects and patients with neutrophilia produced superoxide anion (O₂ ⁻) in vitro at similar rates in the absence of stimulation and exhibited comparably increased rates of O₂ ⁻ production during the initial 1 h of incubation with opsonized zymosan. In the presence of opsonized zymosan, the rate of O₂ ⁻ production by eosinophils was constantly high for 3 h, whereas the rate of production by neutrophils fell by more than 65% after 1 h. Consequently, the amount of superoxide produced by phagocytizing leukocytes was twofold higher for eosinophils than for neutrophils at 3 h. O₂ ⁻ production by cell-free sonicates of zymosan-stimulated eosinophils and neutrophils exhibited the same preference for NADPH over NADH. One mM sodium azide significantly decreased the generation of O₂ ⁻ by phagocytizing eosinophils, but lacked an effect on neutrophils. The prolonged release of O₂ ⁻ by eosinophils engaged in phagocytosis may contribute both to their unique microbicidal profile and to the capacity of eosinophils to injure host tissues in some eosinophilic syndromes.