IFNB1 and susceptibility to pneumonia measurement: Ectopic N protein expression in lung tissues led to DNA damage, apoptosis, cytosolic DNA accumulation, upregulation of IFNβ, IL-6, and NKG2D ligands, lung injury, and pneumonia to a greater extent in older mice than in younger mice (Fig. 8d, e, and Supplementary Fig. 8a–c).