Effect of IL-18 on the release of IL-6 and its soluble receptors: sIL-6Ralpha and sgp130 by human neutrophils.

The biological activities of IL-18 include its ability to induce the production of inflammatory cytokines such as IL-1 or IL-8 by immunocompetent cells. Our previous study demonstrated that rhIL-18 induces IL-1beta and, to a lesser exted, the secretion of IL-1beta regulatory proteins involving interleukin-1 receptor antagonist (IL-IRa) and soluble interleukin-1 receptor II (sIL-1RII) by neutrophils (PMN), suggesting a significant role of IL-18 in the reactions mediated by IL-1beta. In this study, we estimated the effect of rhIL-18 on the induction of IL-6 and its soluble receptors - sIL-6Ralpha and sgp130 by these cells. Results obtained indicate that IL-18 is a promising candidate for the enhanced secretion of IL-6 by human neutrophils. In contrast, we have not found a significant effect of IL-18 on the release of both soluble receptors of IL-6. The influence of IL-18 on the IL-6 production by PMN appears to indicate a potential role of IL-18 in the early steps of the inflammatory cascade and other immune reactions mediated by IL-6.