STAT4-mediated signaling plays a key role in the development of AHR and non-eosinophilic inflammation in the Th2 asthma model. Evaluations (n = 5 each group) were performed twice 48 h after the final allergen challenge. *, P < 0.05 compared to mice sensitized with PBS; **, P < 0.05 versus the other groups; ***, P < 0.05 versus the WT_PBS group. Methacholine AHR (A) and BAL cellularity (B) in STAT4-/- and WT (BALB/c) mice. (H&E staining, original magnification ×100). a, WT_PBS; b, STAT4-/-_PBS; c, WT_OVA/alum; d, STAT4-/-_OVA/alum. (C) Levels of IL-13 (upper left panel), TGF-β1 (upper right panel), and IL-12 (lower panel) in the STAT4-/- and WT control mice. (D) IFN-γ-producing CD11b+ cells in the lungs of the STAT4-/- and WT control mice.