While R. equi-infected Tbk1-/- BMDMs had no difference in expression of the pro-inflammatory cytokine Il1b compared to controls (Fig 4C), they showed almost no induction of Ifnb, Isg15 and Ifit1 at 4- and 8h after infection (Fig 4D), indicating that TBK1 is required for induction of a type I IFN response following infection with R. equi. This evidence concerns the gene ISG15 and infection.