IFNAR1 and bronchopneumonia: The bacterial burden in the spleen and liver was negligible and similar in both genotypes at 12 h p.i. Analysis of lung sections 48 and 72 h p.i. showed more severe bronchopneumonia in Ifnar1-/- mice compared to WT controls, as revealed by a higher overall histopathology score comprising airway inflammation, intralesional bacterial burden and neutrophil infiltration (Fig 1E and 1F).