G9a is required for the development of protective Th2 cell responses in the absence of IFN-γ. G9a^fl/fl, G9a^−/−, and G9a^−/− mice treated with α–IFN-γ were infected with T. muris and sacrificed 21 d later. (A) mLN cells were restimulated with T. muris antigen for 72 h and analyzed by ELISA for production of IFN-γ and IL-13. (B) Ifng and Il13 gene expression in large intestinal tissue was analyzed by qPCR. (C) mLN cells were restimulated with T. muris antigen or monoclonal antibodies against CD3 and CD28 (α-CD3/CD28) for 72 h and analyzed by intracellular cytokine staining for production of IFN-γ. (D) Goblet cell hyperplasia and intestinal architecture was analyzed by staining cecal sections with periodic acid–Schiff’s. Bars, 50 µm. (E) Worm burdens were determined microscopically. Data are representative of three independent experiments (n = 12). ND, not detected. Asterisks indicate P < 0.05. Error bars indicate SEM.