Potentiation of neutrophil function by recombinant DNA-produced interleukin 1a

The effect of interleukin 1a (IL-1a) produced by E. coli-derived recombinant DNA was evaluated on various parameters of human neutrophil function. IL-1a alone stimulated neutrophil hydrogen peroxide production in a dose-dependent manner, but the rate was much lower than that of opsonized zymosan. IL-1a induced release of specific granule contents, but not azurophilic granule contents. Cytochalasin B did not augment the rate of release. IL-1a was chemotactic for neutrophils at the optimal concentrations of 0.1-10 ng/ml. Pretreatment of the neutrophils with IL-1a augmented neutrophil oxygen radical production induced by opsonized zymosan, and this synergistic effect was evident as early as 10 min after IL-1a was added to the neutrophil culture. Phagocytosis of opsonized particles by neutrophils, and degranulation induced by opsonized zymosan were also enhanced by IL-1a in a dose-dependent manner. The present results suggest that IL-1a is weak as a direct activator of neutrophil function and that IL-1a in vivo may augment the response of neutrophils to other stimulators such as foreign bodies.