TGFB1 and chronic obstructive pulmonary disease: Our data for TGF-β1 agree with some previous studies22, 23 but not others.24, 25 The latter studies found increased TGF-β1 expression in the small airway and alveolar epithelial cells, but when the control subjects used for the study are classified according to current GOLD criteria using FEV1/FVC ratios, many would be reclassified as having COPD.24