TGFB1 and idiopathic pulmonary fibrosis: 2012). Transforming growth factor‐β (TGF‐β) is a key cytokine that has been implicated in both epithelial repair and matrix deposition and there is considerable evidence that it plays a central role the pathogenesis of fibrotic diseases. Increased levels of TGF‐β have been found in fibroblastic foci of IPF patients (Broekelmann et al. 1991), overexpression of active TGF‐β induces fibrosis (Sime et al. 1997), whereas inhibition has prevented fibrosis (Wang et al. 1999) in animal models of disease.