Expression of Th1 and Th2 immunoregulatory cytokines by human eosinophils.

Besides cytotoxic mediators, human eosinophils can produce proinflammatory and anti-inflammatory cytokines, as well as growth factors and chemokines. The demonstration that eosinophils from patients could produce IL-5, IL-4 and IL-2 suggested their participation in the regulation of immune response. In the present work, we have examined the presence of Th1 (IFN-gamma, IL-2) and Th2 (IL-4, IL-5, IL-10 and IL-13) cytokines in eosinophils from patients or donors by intracellular flow cytometry, and by immunocytochemistry. Whereas almost 100% eosinophils expressed intracellular IFN-gamma, IL-2 and IL-10, the expression of IL-4, IL-5 and IL-13 is more variable and increased in patients versus donors. The differential release by eosinophils of Th2 versus Th1 cytokines is suggested both by the decrease of the intracellular content after culture, restricted to IL-4, IL-5 and IL-13, associated with an accumulation of IL-4 and IL-5 in the presence of Brefeldin. These results indicate that, through the preferential release of Th2 cytokines, human eosinophils can participate in the polarization of the immune response.