Among major inflammatory mediators, leukotrienes (LTs) are a class of closely structurally related lipid compounds that derive from the 5-lipoxygenase pathway of arachidonic acid metabolism. The LTs family includes LTA4, LTB4 and LTC4/D4/E4 (cysLTs), all of which are potent leukocytes chemoattractants and activators. LTA4, an unstable intermediate, can be further metabolized to LTB4 or cysLTs. LTC4 and LTD4 both have very short half-lives, whereas LTE4 appears to be most stable. The effects of mediators occur after their interaction with receptors.