[Interleukin-5-induced generation of superoxide by eosinophils in asthma]

Superoxide generation was assessed in highly purified eosinophils (> 99.0% pure) with a flow cytometer. Eosinophils from patients with asthma were collected by centrifugation of leukocytes on Percoll density gradients, followed by negative immunoselection with anti-CD16 monoclonal antibodies. For comparison, highly purified neutrophils (< 99.5% pure) were collected by a similar method with anti-CD9 monoclonal antibodies. After incubation with a fluorescent probe, the cells were stimulated with various concentrations of PAF, PMA or various cytokines. Both eosinophils and neutrophils generated superoxide dose-dependently in response to PAF and PMA. Eosinophils generated superoxide in response to IL-3 and IL-5 (maximum concentration was 50 ng/ml), but neutrophils did not. IL-5-induced superoxide generation was lower in the presence of IL-5 antibodies. After stimulation with PMA, superoxide generation was significantly higher in neutrophils than in eosinophils (p < 0.05). There were no significant differences in PAF-induced or GM-CSF-induced superoxide generation between eosinophils and neutrophils. After stimulation with the optimal concentration of IL-5 or PMA, eosinophils with a lower density generated significantly more superoxide than those with a higher density.