Recently, resolution of inflammation has been redefined as an active process, where anti-inflammatory lipid mediators, such as lipoxins, resolvins, and protectins, termed "specialized proresolving mediators" (SPMs), are biosynthesized.In experimental murine models, SPMs have beneficial effects in inflammatory lung disease such as bronchial asthma, acute lung injury and pneumonia.In humans, SPMs also play a significant role in inflammatory disease, such as severe asthma.Eosinophils are capable of pro-inflammatory lipid mediators, such as synthesizing leukotriene (LT) B4, LTC4, which act as a positive feedback machinery in eosinophilic inflammation.Recently we showed that protectin D1 (PD1), which is one of SPMs biosynthesized from docosahexaenoic acid (DHA) enriched in fish, in nanomolar concentrations, suppressed chemotaxis and modulated the expression of the adhesion molecules in human eosinophils.We also investigate the endogenous synthesizing capacity of PD1 in human eosinophils in the presence of DHA using liquid chromatography-tandem mass spectrometry-based lipidomic analysis.Interestingly compared with the eoshinophils harvested from healthy subjects, we observed a prominent decrease in the biosynthesis of PD1 by the cells from patients with severe asthma, even in presence of DHA.These observations are a first indication that activated human eosinophils represent a major source of PD1, which can act as a self-resolving machinery in eosinophilic inflammation, whereas production of PD1 in human eosinophils could be impaired in severe asthma.