T-cell proliferationand Th skewingareimpaired in p38αβ^Y323F T cells. (A) T cells from mice of the indicated genotypes were stimulated with various concentrations of plate-bound α-CD3 and α-CD28 (2 μg/mL) for 48 hours and proliferation assessed by [³H]thymidine incorporation. The figure represents the mean ± SEM from 3 independent experiments. (B) WT (solid line) and p38αβ^Y323F (dotted line) T cells were skewed toward Th1 for 6 days, rested overnight, and restimulated with α-CD3 or PMA and ionomycin (P + I) for 6 hours. IFN-γ expression was detected by intracellular staining. The gray filled histogram indicates unstimulated WT T cells. (C) Percentage of WT (black bar) and p38αβ^Y323F (white bar) Th1 IFN-γ–positive cells from 3 independent experiments. (D) Th2- and (E) Th17-differentiated WT and p38αβ^Y323F CD4⁺ T cells were stimulated as indicated and after 6 hours were intracellularly stained for IL-10 and IL-4 (D) or IL-17 and IFN-γ (E). The numbers indicate the percentage of cells in the corresponding quadrant. (F-G) Summary of IL-4– and IL-10–positive (F) or IL-17–positive (G) WT (black bars) and p38αβ^Y323F (white bars) effectors from 3 independent experiments. Data are mean ± SEM. N.S. indicates not significant.