Figure 4. SIGIRR suppresses Th17 differentiation and expansion through IL-1R signaling.

(A) Naïve wild-type and Il1r1^−/− CD4⁺ T cells (CD4⁺CD44^low) were polarized to Th17 cells (TGFβ+IL-6 on anti-CD3 and anti-CD28 coated plates) in the presence and absence of IL-1β, followed by ELISA for IL-17 and IL-22. (B) Naïve wild-type and Sigirr^−/− CD4⁺ T cells (CD4⁺CD44^low) were polarized to Th17 cells (TGFβ+IL-6 on anti-CD3 and anti-CD28 coated plates) in the presence and absence of IL-1β, followed by intracellular cytokine staining for IL-17 and IFN-γ. While IL-1β promoted Th17 cell differentiation in both WT and Sigirr^−/− T cells, addition of IL-1β resulted in a significantly higher IL-17-positive population in Sigirr^−/− T cells than that in WT T cells. (C) Real-time PCR analysis of relative expression of IL-17, IL-22, IL-21, IL-23R, ROR-γt, IL-10 and IRF4 in wild-type and Sigirr^−/− Th17 cells as compared to the naïve T cells. Data are representative of at least three (A–C) separate experiments. Error bars (AC), s.e.m. *, p<0.05; **.p<0.01 (two tailed t-test).