Effect of iloprost on bleomycin-induced pulmonary inflammation and fibrosis. Histological analysis of lungs in the mice treated with bleomycin and those treated with bleomycin+iloprost. Mice were killed at day 14, lungs were removed, inflated with 1 ml of 10% formalin. In the mice treated with PBS (no iloprost) or PBS+iloprost, there was normal alveolar structure (A and B). In the mice treated with bleomycin (no iloprost), there was more accumulation of leukocytes, distortion of alveolar architecture, and deposition of collagen (C and E), compared with the mice treated with bleomycin+iloprost (D and F). Panels A-D, H&E staining; Panel E-F, Masson's trichrome staining.