Sentinels at the wall: epithelial-derived cytokines serve as triggers of upper airway type 2 inflammation

Recent evidence has demonstrated an expanding role of respiratory epithelial cells in immune surveillance and modulation. Studies have been focusing on the earliest events that link epithelial injury to downstream inflammatory responses. Cytokines produced by and released from respiratory epithelial cells are among these early trigger signals. Epithelial-derived cytokines, namely thymic stromal lymphopoietin (TSLP), interleukin (IL)-25, and IL-33, have come to the forefront of recent investigations. Each of these 3 cytokines has been implicated in chronic rhinosinusitis (CRS), asthma, and atopy. Herein we review studies elucidating the roles of epithelial-derived cytokines in the pathobiology of upper airway disease, with particular emphasis on type 2 inflammatory conditions.