To confirm that type I IFN signaling is activated by K. pneumoniae also in vivo, we examined the lung tissue 12 h p.i. Expression of the ISGs Mx1, Ifit1 and Isg15 was induced in WT but not Ifnar1-/-mice (Fig 3A) corroborating the results obtained using infection of macrophages. Here, IFIT1 is linked to infection.