Immunological Regulation by Bioactive Lipids

Mast cells originate from hematopoietic stem cells and undergo terminal maturation in the extravascular tissues, in which they are ultimately resident. Mast maturation, phenotype, and function are dictated by the local microenvironment, which has a significant influence on the ability of mast cells to recognize and respond to stimuli. Activation of mast cells can lead to the release of three distinct classes of mediators, including preformed mediators stored in secretory granules, newly transcribed cytokines and chemokines, and de novo-synthesized bioactive lipid mediators. It is currently recognized that bioactive lipids such as arachidonic acid metabolites (prostaglandins and leukotrienes) released from mast cells modulate innate and adaptive immune responses both directly and indirectly through communication with other microenvironmental immune cells or stroma cells. Moreover, mast cells express a variety of lipid receptors and, if activated by bioactive lipids such as arachidonic acid, ω3 fatty acids, lysophospholipids, and their metabolites, can alter the release and production of other mediators including histamine, cytokines, and chemokines, and thereby alter homeostatic or pathophysiological responses. This review focuses on newly identified functional aspects of bioactive lipids with regard to their immune regulation and functional outcomes in both homeostasis and allergic disease.