Enhanced TGFβ1 immunostaining and collagen production in bleomycin treated Tr+ TGFβ1 transgenic mice. A, B. To determine the role of TGFβ1 in the induction of lung fibrosis in mice treated with bleomycin, immunostaining for active TGFβ1 was performed as previously described. Shown are representative micrographs following immunostaining for TGFβ1 in the lung of bleomycin treated, Tr- wild type (A) and Tr+ TGFβ1 transgenic (B) mice. Expression of TGFβ1 is present in both tissue specimens but is substantially enhanced in the Tr+ TGFβ1 transgenic mice. C. Total collagen was determined by hydroxyproline assay as previously described. Collagen production was significantly enhanced in all bleomycin-wounded mice versus control PBS exposed, and in particular collagen deposition has been found higher in Tr+ TGFβ1 transgenic mice than in Tr- Wild Type ones. BLM, Bleomycin.