Lung fibroblasts from patients with IPF that were exposed to TGF-β1 generated H2O2; these fibroblasts were cytotoxic to pulmonary epithelial cells in co-cultures, and this cytotoxic effect was inhibited by the addition of catalase, or by blockade of H2O2 generation [295]. This evidence concerns the gene TGFB1 and idiopathic pulmonary fibrosis.