IRF9 and infection: Furthermore, the role of type I IFN signaling was confirmed by this approach for genes including Oas1, Ifit3 and Ifng, but additionally Irf9 was shown to be higher (Fig 5D) in the infected Ifnar1-/- as compared to the infected WT mice at day 1 post infection when the bacterial loads were similar (Fig 3A), but lower at day 3 in the infected Ifnar1-/- when the bacterial loads were reduced (Fig 3A).