STAT1 and infection: Ddx3xfl/flLysMCre BMDMs showed a significant reduction in secretion of IFN-β and delayed activation of STAT1 (P-STAT1 levels) compared with Ddx3xfl/fl BMDMs upon IAV and IAV–ΔNS1 infection, further establishing a role for DDX3X in IAV-induced type I IFN responses (Fig. 3D, Fig. S5, A and B).