With reference to the epithelial–mesenchymal transition in conditions of pulmonary fibrosis, in the study by Fei Jiang et al., it was shown that incubation of human alveolar epithelial cells (A549) with TGF-β (5 ng/mL) led to an increase in the expression of mesenchymal markers (N-cadherin and vimentin) in them with a corresponding suppression of the expression of epithelial markers (E-cadherin). Here, TGFB1 is linked to pulmonary fibrosis.