Introduction:     Interleukin 27 (IL‑27) is a cytokine secreted mostly by antigen‑presenting cells. It is important for the immune polarization of T helper‑1 (Th1) cells, and its role in interstitial lung diseases (ILDs) and lung cancer has been investigated.

Objectives:     We assessed IL‑27 expression in the lower airways of patients with selected ILDs and early‑stage non–small cell lung cancer (NSCLC).

Patients and methods:     IL‑27 concentrations were examined by an enzyme‑linked immunosorbent assay in bronchoalveolar lavage (BAL) fluid supernatants collected from patients with pulmonary sarcoidosis (PS; n = 30), extrinsic allergic alveolitis (EAA; n = 14), idiopathic pulmonary fibrosis (IPF; n = 12), nonspecific interstitial pneumonia (NSIP; n = 14), and NSCLC stages I to IIa (n = 16) with peripheral localization, and in controls (n = 14). The major lymphocyte subsets in BAL fluid were phenotyped, and intracellular IL‑27 expression was evaluated by flow cytometry.

Results:     IL‑27 concentrations in BAL fluid supernatants were significantly increased in Th1‑mediated conditions such as EAA and PS, but not in IPF or NSIP. The highest IL‑27 levels (median [SEM], 16.9 [17.5] pg/ml) were reported for NCSLC, and the lowest—for controls (median [SEM], 0.4 [0.2] pg/ml). IL‑27 was undetectable in corticosteroid‑treated patients with PS. Both CD4+ and CD8+ lymphocytes were positive for IL‑27; they were a possible local source of IL‑27 because the cytokine levels were positivelysignificantly correlated with the total number of lymphocytes, including CD4+ cells.

Conclusions:     Our results support the Th1‑linked activity of IL‑27in ILDs. Early‑stageNSCLC is characterizedby high IL‑27expression in the lower airways. IL‑27 is produced by a high percentage of CD4+ and CD8+ cells in BAL fluid, both in patients and controls.