It was hypothesized that the suppressive effect of diosgenin (1) on the intestinal T helper (Th)2 responses is associated with an enhancement of the regulatory T-cell immunity. Ovalbumin (OVA)-sensitized BALB/c mice were gavaged daily with 1 and received repeatedly oral OVA challenges to induce intestinal allergic responses. The expression of Th2-and Treg-related cytokines and transcription factors was examined by immunohistochemical staining and RT-PCR. Administration of 1 markedly attenuated the intestinal expression of interleukin (IL)-4 and GATA3. In addition, administration of 1 reversed the diminished density of intestinal Foxp3+ cells induced by OVA oral challenges and enhanced the expression of IL-10 by Foxp3+ cells markedly. These results suggest that the suppressive effect of 1 on allergen-induced intestinal Th2 responses is closely associated with an up-regulation of the regulatory T-cell immunity in the inflammatory site.
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