Sei Won Kim,1,* Chin Kook Rhee,2,* Ki Uk Kim,3 Sang Haak Lee,4 Hun Gyu Hwang,5 Yu Il Kim,6 Deog Kyeom Kim,7 Sang Do Lee,8 Yeon-Mok Oh,8 Hyoung Kyu Yoon1 On behalf of the KOLD Study Group 1Division of Pulmonary, Department of Internal Medicine, Yeouido St Mary’s Hospital, 2Division of Pulmonary, Allergy and Critical Care Medicine, Department of Internal Medicine, Seoul St Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, 3Department of Internal Medicine, Pusan National University, School of Medicine, Busan, 4Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, St Paul’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, 5Department of Internal Medicine, Soonchunhyang University Gumi Hospital, Gumi, 6Division of Pulmonology, Department of Internal Medicine, Chonnam National University Hospital, Gwangju, 7Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, SMG-SNU Boramae Medical Center, Seoul National University College of Medicine, 8Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea *These authors contributed equally to this work Background: Interleukin (IL)-33 promotes T helper (Th)2 immunity and systemic inflammation. The role of IL-33 in asthma has been widely investigated. IL-33 has also been suggested to play an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). This study investigated the clinical significance and usefulness of plasma IL-33 level in patients with COPD. Methods: A total of 307 patients with stable COPD from 15 centers, who were in the Korean Obstructive Lung Disease cohort, were enrolled in this study. Plasma IL-33 levels were measured by enzyme-linked immunosorbent assay. We analyzed the association between IL-33 level and other clinical characteristics related to COPD. We also examined the features of patients with COPD who exhibited high IL-33 levels. Results: IL-33 levels varied, but were very low in most patients. Eosinophil count was significantly correlated with a plasma IL-33 level. In addition, old age and current smoking were related to a low IL-33 level. Significantly more patients with a higher IL-33 level had chronic bronchitis compared with those with a low IL-33 level. Conclusion: Plasma IL-33 level in patients with stable COPD was related to eosinophil count and chronic bronchitis phenotype. Further studies are needed to identify the precise mechanisms of IL-33/ST2 pathway in patients with COPD. Keywords: biomarker, cytokine, interleukin-33, eosinophil, pathogenesis, chronic bronchitis
