The important role that TGF-β may play in this disorder can be seen in studies that demonstrate that TGF-β is a critical mediator of pulmonary fibrosis after bleomycin injury (Nakao et al, 1999; Yehualaeshet et al, 2000) and that transgenic overexpression in the lung or high-dose adenoviral TGF-β1 transfer causes progressive pulmonary fibrosis in vivo (Sime et al, 1997; Kelly et al, 2003; Lee et al, 2004) and IPF-like fibroblastic foci in in vitro explants (Xu et al, 2003). The gene discussed is TGFB1; the disease is pulmonary fibrosis.