Leukotriene E4
Leukotriene E4 (LTE) is a cysteinyl leukotriene involved in inflammation. It is known to be produced by several types of white blood cells, including eosinophils, mast cells, tissue macrophages, and basophils, and recently was also found to be produced by platelets adhering to neutrophils. It is formed from the sequential conversion of LTC to LTD and then to LTE, which is the final and most stable cysteinyl leukotriene. Compared to the short half lives of LTC and LTD, LTE is relatively stable and accumulates in breath condensation, in plasma, and in urine, making it the dominant cysteinyl leukotriene  detected in biologic fluids. Therefore, measurements of LTE, especially in the urine, are commonly monitored in clinical research studies. Increased production and excretion of LTE has been linked to several respiratory diseases, and urinary LTE levels are increased during severe asthma attacks and are especially high in people with aspirin-induced asthma, also known as Samter’s Triad or aspirin-exacerbated respiratory disease (AERD). Studies have suggested that LTE works through its own distinct receptor, and although one has not yet been discovered, research is ongoing to isolate and characterize an LTE-specific receptor.