Histology of lungs. Lungs of Wt (A,C) and PAI-1^-/- mice (B,D) at 24 hours (panels A-B) and 48 hours (panels C-D) after infection. Hematoxylin and eosin (HE) staining; original magnification, × 20. No difference was seen in the composition of inflammation between Wt and PAI-1^-/- mice.