IFNAR1 and infection: To determine whether IFN-I signaling is required for BBB integrity in vivo, we determined the bacterial loads in the brain and spleen of WT and Ifnar–/– mice that were intravenously infected with A. baumannii. Twenty hours after infection with A. baumannii, the bacterial loads in the brain and spleen were significantly greater in Ifnar–/– mice than in WT mice (Fig 4D and 4E).