As the main cell types involved in lung fibrosis are epithelial cells, fibroblasts, and immune cells, we cultured the human alveolar basal epithelial adenocarcinoma cell line A549, human small airway epithelial cells, human pulmonary fibroblasts, and human immune cells (PBMC) with or without 10 ng/ml of recombinant active TGF-β1 (a standard concentration used in tissue culture experiments6,62–64) for five days. This evidence concerns the gene TGFB1 and pulmonary fibrosis.