The stimulation of lung fibroblasts from IPF and normal subjects with 5 ng/mL of TGF-β induced a change in cell morphology and an intensive expression of α-SMA, and we found that this stimulation was less pronounced in the cells derived from IPF patients compared to those from control donors (p < 0.05 vs. p < 0.001). This evidence concerns the gene ACTA1 and idiopathic pulmonary fibrosis.