Serum IL-36 cytokines levels in idiopathic pulmonary fibrosis and connective tissue disease-associated interstitial lung diseases

Interleukin-36 (IL-36) family is associated with several fibrosis-related disorders and connective tissue diseases. However, their expression in idiopathic pulmonary fibrosis (IPF) and connective tissue disease-interstitial lung disease (CTD-ILD) is unknown.We included 19 CTD-ILD patients, 16 IPF patients, and 27 healthy control subjects. Determination of serum concentrations of IL-36α, IL-36γ and IL-36 receptor antagonist (IL-36Ra) was performed by ELISA. The value of biomarkers for the diagnosis and assessment of ILD was assessed by lung function tests and high-resolution computed tomography.Serum concentrations of IL-36α and IL-36γ in patients with CTD-ILD and IPF were significantly higher than that in healthy controls, whereas serum IL-36Ra concentrations were not significantly different between the 3 groups. Increased IL-36 levels correlated with disease severity in IPF patients. ROC curve analysis showed that the AUC was 0.9931 for IL-36α and 0.8194 for IL-36γ in IPF group. In CTD-ILD group, the AUC was 0.9825 for IL-36α and 0.7973 for IL-36γ.We demonstrated an imbalance in the agonist and antagonist profiles of IL-36 cytokines in ILD. IL-36 cytokines may be a new diagnostic or therapeutic target in ILD, especially in IPF.