Effects of bleomycin on lung inflammation and macrophage activation. Lung sections, prepared 0 d (CTL), 3 d, 7 d, and 28 d after exposure of mice to bleomycin (3 U/kg), were immunostained with antibody to CD11b (left panels, 100× magnification), iNOS (center panels, 400× magnification), and Arg-1 (right panels, 400× magnification). Binding was visualized using a Vectastain kit. Representative sections from 3 mice/treatment group are shown.