Mice were infected with PR8 (A/PR/8/34, 100 pfu) via oropharyngeal administration. A) Morbidity as measured by weight loss. Each time point is representative of 8 mice from 2 experiments. B) Lung viral load was measured by quantitative qRT-PCR for the influenza M1 gene. Each point represents an individual mouse. n=8 mice per group from 2 independent experiments. C) Histopathology from day 10 after infection demonstrates extensive inflammation in wild type (53) mice in comparison to very mild, very focal inflammation in the Il-22ra2−/− mice. D) Total affected vs. unaffected areas in infected wildtype and il-22ra2−/− mice. E) Slides were scored blindly for bronchiolitis and alveolitis as described in materials and methods. N= at least 8 for each figure, with each experiment being reproduced at least twice. Statistical analysis was performed using one way ANOVA with Tukey’s post-hoc test (A,B) or Students T test. *** p<0.001, ****p<0.0001.