IL18R1 and idiopathic pulmonary fibrosis: IL-18 levels in serum and BAL of patients with IPF were higher than those in control subjects, and while IL-18Rα was expressed in bronchial epithelium and alveolar macrophages in control subjects, it was found to be strongly expressed in interstitial cells, especially the fibroblastic foci, in patients with IPF [179].