IL-12–induced phosphorylation of Stat4 is impaired in Tyk2^−/− DCs. (A) Isolated CD11c⁺ DCs from WT splenocytes or Tyk2^−/− splenocytes were analyzed for the expression of IL-12Rβ1 and IL-12Rβ2 by FACS. Representative histograms are shown (n = 3). Dashed lines indicate the staining with isotype-matched control antibodies. (B) Isolated CD11c⁺ DCs from WT splenocytes or Tyk2^−/− splenocytes were cultured with CpG ODN (10 μg/mL) for 3 days. Intracellular staining for Stat4 was performed and analyzed by FACS. As controls, freshly isolated CD11c⁺ DCs from WT splenocytes or Tyk2^−/− splenocytes were stained for Stat4. Representative histograms of anti-Stat4 staining gated on CD11c⁺ cells are shown (n = 4). (C) Isolated CD11c⁺ DCs from WT splenocytes or Tyk2^−/− splenocytes were cultured with CpG ODN for 3 days. After cells were washed and rested in fresh medium for 12 hours, cells were stimulated with IL-12 (20 ng/mL) for 20 minutes and intracellular staining for the phosphorylated form of Stat4 was performed and analyzed by FACS. Representative histograms of anti–phospho-Stat4 staining gated on CD11c⁺ cells are shown (n = 4).