The prostaglandin D <inf>2</inf> receptor 2 pathway in asthma: A key player in airway inflammation 11 Medical and Health Sciences 1107 Immunology 11 Medical and Health Sciences 1102 Cardiorespiratory Medicine and Haematology

© 2018 The Author(s). Asthma is characterised by chronic airway inflammation, airway obstruction and hyper-responsiveness. The inflammatory cascade in asthma comprises a complex interplay of genetic factors, the airway epithelium, and dysregulation of the immune response. Prostaglandin D 2 (PGD 2 ) is a lipid mediator, predominantly released from mast cells, but also by other immune cells such as T H 2 cells and dendritic cells, which plays a significant role in the pathophysiology of asthma. PGD 2 mainly exerts its biological functions via two G-protein-coupled receptors, the PGD 2 receptor 1 (DP 1 ) and 2 (DP 2 ). The DP 2 receptor is mainly expressed by the key cells involved in type 2 immune responses, including T H 2 cells, type 2 innate lymphoid cells and eosinophils. The DP 2 receptor pathway is a novel and important therapeutic target for asthma, because increased PGD 2 production induces significant inflammatory cell chemotaxis and degranulation via its interaction with the DP 2 receptor. This interaction has serious consequences in the pulmonary milieu, including the release of pro-inflammatory cytokines and harmful cationic proteases, leading to tissue remodelling, mucus production, structural damage, and compromised lung function. This review will discuss the importance of the DP 2 receptor pathway and the current understanding of its role in asthma.