STAT-1 signaling is required for IFNβ-induced apoptosis. (A) wt and STAT-1^−/− DCs were treated with the cytokine cocktail in the presence or absence of IFNβ (1000 IU/mL) for 30 minutes. DCs were fixed and permeabilized followed by intracellular staining for phospho–STAT-1 and total STAT-1; (B-C) wt and STAT-1^−/− DCs were treated with the cytokine cocktail in the presence or absence of IFNβ (B) or IFNγ (C). Forty-eight hours later, DCs were subjected to apoptosis assays. Data are representative of 2 independent experiments with triplicate samples.