The methyltransferase activity of G9a is required for silencing of IL-17A. (A) CD4⁺ Th cells isolated from G9a^fl/fl and G9a^−/− mice were stimulated for 6 d under neutral, Th1, or Th2 conditions and analyzed for IL-17A production by ELISA. (B and C) Expression of IL-17A was determined by ELISA of supernatants from T. muris antigen-restimulated mLN cultures (B) and qPCR of mRNA isolated from intestinal tissue (C). (D and E) CD4⁺ Th cells isolated from G9a^fl/fl and G9a^−/− mice were stimulated for 6 d under neutral, Th1, and Th2 conditions in the presence or absence of 500 nM BIX-01294 (BIX) and analyzed by ELISA for expression of IL-13 and IFN-γ (D) or IL-17A (E). (F) CD4⁺ Th cells isolated from G9a^fl/fl and G9a^−/− mice were stimulated for 6 d under neutral, Th1, and Th2 conditions and analyzed by ChIP for H3K9me2. Data in A–E are representative of three independent experiments and data in F is from two independent experiments. Asterisks indicate P < 0.05. Error bars indicate SEM.