Human peripheral blood eosinophils express and release interleukin-8.

Eosinophils can synthesize various cytokines. We demonstrate that interleukin-8 (IL-8) mRNA and protein are constitutively expressed by freshly isolated resting human eosinophils. Most of the patients with bronchial asthma or atopic dermatitis show evidence for up-regulated IL-8 protein expression in eosinophils but not in neutrophils, suggesting that an eosinophil-specific cytokine may act in these patients. To investigate whether the intracellular IL-8 can be released, eosinophils were stimulated by different cytokines and platelet-activating factor (PAF). Priming with granulocyte/macrophage-colory-stimulating factor and a subsequent 25-min stimulation with RANTES or PAF resulted in release of IL-8 from highly purified human eosinophils in vitro.