IL-2 contributes to the IL-5 response in granulomas from mice infected with Schistosoma mansoni

Th cells within the granulomas of murine schistosomiasis mansoni produce IL-5, which is essential for granuloma eosinophil growth and development. The mechanisms regulating granuloma IL-5 production are unknown. The granulomas also make IL-2 in small quantities. rIL-2 therapy stimulates eosinophilia and IL-5 synthesis. Therefore, we studied the effect of IL-2 on IL-5 production within the liver granulomas of murine Schistosoma mansoni. Dispersed granuloma cells and intact granulomas cultured in vitro released IL-5. Adding anti-IL-2 or anti-IL-2R to the cultures, to block IL-2 activity, significantly inhibited IL-5 production. However, supplementing the cultures with small quantities of rIL-2 markedly stimulated IL-5 release in a dose-dependent fashion. Blocking anti-IL-4 mAb had no effect. Also, granuloma T cells were isolated by FACS. These highly purified T cells produced IL-5 both in the presence and absence of plate-bound anti-CD3. Once again, the IL-5 production was dependent on IL-2. The requirement of IL-2 for normal IL-5 production was not dependent on an IL-2-induced expansion of the IL-5-producing, T lymphocyte population. Thus, IL-2 mediates T cell interactions within the granuloma that regulate granuloma IL-5 secretion.