Suppression of IL-17 by IFN- γ is associated with IDO.

<p>(a) CD4⁺ T cells isolated from wild type (WT) C57BL/6 (B6) mice and IFN-γ knock out (KO) B6 mice. The cells were cultured in Th17-polarizing conditions (anti CD3 mAb, anti CD28 mAb, anti IFN-γAb, anti IL-4 Ab, TGF-β, IL-6). Non-CD4 cells were cultured with media only or 100 ng/ml of recombinant IFN-γ. After 72hours, cells were washed and only APCs were irradiated at 3000 rad. After Th17 cells and APC/APC_IFN-γ were co-cultured (1∶1) for 16 hrs, the culture supernatant was measured for IL-17 ELISA (right). (b) Splenocytes derived from IFN-γ KO mice were cultured solely or with combined condition with 10 ng/ml of IL-23, 50 ng/ml of IFN-γ, 100 µM 1-MT for 72 hrs. IFN-γ and 1-MT was pretreated. (c) IL-17 mRNA expression of Th17 polarized cells derived from B6 and IDO KO mice splenocyte. (d) Splenocytes derived from IL-1Ra KO mice were cultured solely or with combined condition with 10 ng/ml of IL-23, 50 ng/ml of IFN-γ, 100 µM 1-MT for 72 hrs. IFN-γ and 1-MT was pretreated. ANOVA with post hoc analysis (d,f) was used. Values are presented as the mean ± standard deviation of three independent experiments. *, p<0.05, **, p<0.005 ***, p<0.001.