Sections of lung from patients with idiopathic PAH (IPAH) or with SSc-PAH expressed higher levels of type I interferon receptor 1 (IFNR1) in endothelium, smooth muscle layer, vascular interstitium, and in intravascular inflammatory cells as assessed by immunohistochemistry and Western blotting (117). This evidence concerns the gene IFNAR1 and idiopathic pulmonary arterial hypertension.