Increased type I and III interferon induction in Ifit2−/− and IFNAR−/− lungs after SeV infection. Ifit1 (A), Ifit2 (B), IFN-β (C), and IFN-λ3 (D) mRNA expression in lungs of wt, Ifit2−/−, and IFNAR−/− mice (n = 3 to 7) after SeV infection, measured by real-time RT-PCR. Asterisks indicate statistical significance; n.s., not significant; ND, not detected.