EOSINOPHILOPOIETIC FACTORS PRIME EOSINOPHILS FOR INCREASED INTERLEUKIN-8 GENERATION

Recent studies have identified eosinophils as a cellular source of var ious cytokines, indicating that eosinophils play not only an effector role but also a regulatory role within the allergic inflammatory cell network. Because eosinophilopoietic factors are known to stimulate var ious functions of eosinophils, we examined the effect of interleukin ( IL)-5 on chemoattractant-induced IL-8 generation from eosinophils. Alt hough IL-5 alone induced little or no IL-8 production from eosinophils , short-term preincubation with IL-5 markedly enhanced the eosinophil IL-8 generation caused by C5a plus cytochalasin B (CB). IL-3 also pote ntiated C5a-induced IL-8 generation. Both factors were active at picom olar concentrations. Furthermore, competitive polymerase chain reactio n (PCR) experiments revealed that the enhancement occurred at the pret ranslational level. Since eosinophils in allergic inflammation are bel ieved to be activated by these eosinophilopoietic factors, eosinophil- derived cytokines may play more important roles in the allergic inflam matory cell network than has been previously supposed.