Group 2 innate lymphoid cells and eosinophilic chronic rhinosinusitisTojima, Ichiro; Shimizu, TakeshiCurrent Opinion in Allergy and Clinical Immunology: February 2019 - Volume 19 - Issue 1 - p 18–25 doi: 10.1097/ACI.0000000000000496 RHINITIS, SINUSITIS AND UPPER AIRWAY DISEASE: Edited by Ruby Pawankar and David P. Skoner Abstract Author InformationAuthors Article MetricsMetrics Purpose of review Chronic rhinosinusitis (CRS) is a heterogeneous disease and is recently classified into two phenotypes, eosinophilic CRS (ECRS) and non-ECRS. ECRS is characterized by Th2-biased eosinophilic inflammation, and non-ECRS is characterized by Th1-biased neutrophilic inflammation. Group 2 innate lymphoid cells (ILC2s) rapidly produce large amounts of Th2 cytokines and exert critical roles in Th2-type immune responses. We summarize our current knowledge about the pathogenic roles of ILC2s in ECRS. Recent findings The prevalence of ILC2s is increased in nasal polyps, and it is positively correlated with the number of infiltrating eosinophils. Epithelium-derived cytokines (IL-33, IL-25, and thymic stromal lymphopoietin), cysteinyl leukotrienes, and prostaglandin D2 stimulate the production of Th2 cytokines from ILC2s, which drives eosinophilic inflammation in nasal mucosa. Regulation of ILC2s would be a novel therapeutic approach for the refractory and/or recurrent cases of ECRS. Summary Increased ILC2s play a pivotal role in the pathophysiology of ECRS by producing large amounts of Th2 cytokines, which lead to Th2-type eosinophilic inflammation in nasal polyps. Department of Otorhinolaryngology, Shiga University of Medical Science, Otsu, Japan Correspondence to Ichiro Tojima, MD, PhD, Department of Otorhinolaryngology, Shiga University of Medical Science, Seta-Tsukinowa, Otsu, Shiga 520-2192, Japan. Tel.: +81 77 548 2261;. fax: +81 77 548 2783; e-mail: firstname.lastname@example.org Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.