Leukotriene B4 (LTB4) is a dihydroxy fatty acid derived from arachidonic acid through the 5-LO pathway. It promotes a number of leukocyte functions including aggregation, stimulation of ion fluxes, enhancement of lysosomal enzyme release, superoxide anion production, chemotaxis, and chemokinesis. 12-oxo LTB4 is an initial metabolite of LTB4 formed via the LTB4 12-hydroxydehydrogenase pathway. It is rapidly converted to 10,11-dihydro-12-oxo-LTB4, followed by reduction of the 12-oxo group to give 10,11-dihydro-LTB4. 12-oxo-LTB4 (EC50 = 33 nM) is about 70-fold less potent than LTB4 (EC50 = 0.46 nM) at stimulating Ca2+ mobilization in human neutrophils. It is also significantly less potent than LTB4 at stimulating neutrophil migration with EC50 values of 170 and 2.7 nM for 12-oxo-LTB4 and LTB4, respectively.