Exogenous interleukin-3 enhances IL-4 production by splenic CD4+ cells during the early stages of a Trichinella spiralis infection.

Treatment with recombinant interleukin-3 (rIL-3) augmented IL-4 production of spleen cells in mice infected with Trichinella spiralis. In a previous report, we showed that treatment with rIL-3 accelerated IgE responsiveness in mice. We have examined IL-4 and interferon (IFN)-gamma production by spleen cells from both rIL-3-treated and untreated mice during the early stages of infection. The results indicated that IL-4 production was enhanced in rIL-3-treated mice compared to that in untreated mice. In contrast, there was no difference in IFN-gamma production between the two groups. Augmentation of IL-4 production was dependent on the dose of rIL-3 injected before infection. To examine if the treatment with rIL-3 affects T cell function, spleen cells from mice treated with various doses of rIL-3 were cultured under the stimulation with anti-CD3 (T cell receptor complex) mAb and then assessed for cytokine production. IL-4 production increased depending on the dose of rIL-3, while IFN-gamma production did not. Furthermore, spleen cells were separated by surface markers, Thy1.2, CD4 and CD8. Thy1. 2+ cell population responded significantly to produce IL-4 after anti-CD3 stimulation, when compared with IL-4 production of Thy1.2- cell population. A major producer of IL-4 in T cells was CD4+ cell population but not CD8+ cell population. IL-4 production was suppressed in rIL-3-treated mice injected with anti-CD4 mAb. These results suggest that IL-3 might play a role as Th2 amplifier in immune response to parasite infection.