S100A9 and infection: Although basal transcription of Ifnγ, S100A9 and Lcn2 was similar between mock-infected WT and mock-infected Ifnar1-/- mice (Fig 3A, 3C and 3E), the transcription of Ifnγ and Lcn2 was significantly higher in the ceca of the Ifnar1-/- group, compared to the WT group, after infection with S. Typhimurium alone (Fig 3A and 3E).