In lung tissue from patients with primary pulmonary hypertension, TGF-β1 immunostaining was either faint or absent in both normal and hypertensive vessels, whereas an intense, cell-associated TGF-β3 and a slightly less intense TGF-β2 immunoreactivity were observed in the media and neointimal of the hypertensive muscular arteries as compared with normal arteries of comparable size [26]. This evidence concerns the gene TGFB1 and idiopathic pulmonary arterial hypertension.