Enforced expression of Sox5t and c-Maf induces Th17 cell differentiation even in the absence of Stat3. (A and B) Naive CD4⁺ T cells from CD4^cre Stat3^fl/fl or Stat3^fl/fl mice were co-infected with indicated retroviruses and the expression of IL-21 versus IL-17A was examined as described in Fig. 4 A. Means ± SD of the percentages of IL-17A–producing CD4⁺ T cells are shown on the right. Data are compiled from four (A) or three (B) independent experiments. **, P < 0.01. (C–E) Naive CD4⁺ T cells from CD4^cre Sox5^fl/fl mice and Sox5^fl/fl mice (C) or WT mice and IL-21^−/− mice (D and E) were transfected with siMaf or nonsilencing controls, and then stimulated in Th17 conditions for 24 h (C and D) or 84 h (E). The expression of IL-21 versus IL-17A was examined as described in Fig. 4 A. Means ± SD. Data are compiled from three independent experiments. *, P < 0.05.