Interleukin-11 in idiopathic pulmonary fibrosis: predictive value of prognosis and acute exacerbation.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a fibrotic lung disease with a poor prognosis and unknown aetiology. We have recently clarified the prognostic value of the serum platelet-derived growth factor (PDGF) level in patients with IPF. Interleukin (IL)-11 is a member of the IL-6 family, and in vivo and in vitro studies have suggested that it has profibrotic effects in pulmonary fibrosis. In this study, we investigated the predictive value of the serum IL-11 level in patients with IPF for survival and occurrence of acute exacerbation (AE). METHODS: This retrospective study included 68 patients with IPF diagnosed according to the 2018 guideline. Serum PDGF levels were measured using the Bio-Plex method and serum IL-11 levels using enzyme-linked immune-sorbent assay. Cytokine production per lung volume was evaluated using the serum cytokine/percent predicted forced vital capacity (%FVC) value. RESULTS: Forty-six patients were male and the median age was 67 years. The serum IL-11/%FVC value was significantly correlated with the percent predicted diffusing capacity of carbon monoxide (ρ=-0.518, P<0.001) and modified Medical Research Council score for shortness of breath (mMRC) (ρ=0.335, P=0.006) by Spearman's rank correlation analysis. Multivariate Cox proportional hazard regression analysis revealed that the serum IL-11/%FVC value was a significant prognostic factor after adjustment for the serum PDGF/%FVC value and other clinical parameters including mMRC and lymphocyte percentage in bronchoalveolar lavage [hazard ratio (HR): 88.540, 95% confidence interval (CI): 1.905-4,115.686, P=0.022]. IL-11/%FVC value was also a significant predictor of AE after adjustment for age and PDGF/%FVC (HR: 1,815.443, 95% CI: 10.49-314,109.219, P=0.004). CONCLUSIONS: The serum IL-11/%FVC value was an independent predictor of prognosis and AE occurrence in patients with IPF, and the IL-11 level appeared to show pathophysiologic value in IPF.