Lung histology after bleomycin injury. PAI-1^−/− and WT mice were treated with intratracheal bleomycin (1.15 μg/kg in 50 μL of sterile PBS) on day 0. Subgroups of PAI-1^−/− mice were administered PAI-1(V+P+), PAI-1(V+P-), and PAI-1(V-P+) at 100 μg/injection every 12 hours beginning on day 8 and continuing through day 19. For comparison, groups of bleomycin-injured PAI-1^−/− mice and WT mice received twice-daily intraperitoneal injections of PBS. On day 19, the left lung was fixed, and 5 micron sections were stained using Masson's trichrome (A) or immunostained with antibodies to α-SMA (B) and F4/80 (C). Images of representative sections from 2 mice (Masson trichrome) or a single mouse (immunostaining) in each treatment group are shown. Micrographs for panels A and B were obtained with a Nikon Eclipse E400 microscope (Melville, NY) and a Nikon 10×/0.25 lens (A) and a Nikon 40×/0.65 lens (B) and captured with a Diagnostic Instruments camera and SPOT Basic Version 4.0.8 acquisition software. Micrographs for panel C were obtained with a Nikon Eclipse 80i microscope and a Nikon 20× lens and captured with a Nikon DS-Qi1Mc camera and Nikon NIS-Elements BR 3.10 software.