IFNAR1 and infection: In contrast, using aged animals in an identical infection setting, we observed significantly increased weight loss in Ifnar1−/−, Ifnlr1−/−, and Ifnar1−/−Ifnlr1−/− mice compared with age-matched WT controls (Fig. 1 D), sporadically even leading to lethal disease progression in case of Ifnar1−/−Ifnlr1−/− mice (Fig. S1 G).