LPS-induced DC apoptosis requires IFNβ. (A) IFNβ production by DCs was measured by ELISA 24 hours after treatment with LPS (100 ng/mL; left panel). DCs were treated with LPS (100 ng/mL) and cultured in the presence or absence of neutralizing IFNβ Ab (10 μg/mL) and analyzed 48 hours later for levels of active caspase-3 and apoptosis by FACS (right and middle panels). (B) wt and STAT-1^−/− DCs were treated with LPS (1 μg/mL) and analyzed for caspase-11 mRNA expression by real-time RT-PCR (24 hours), and for levels of active caspase-3 and viability (48 hours) by FACS. (C) wt and caspase-11^−/− DCs were treated and analyzed as described in panel B. Data are representative of 2 independent experiments with triplicate samples.