Is eosinophil chemotactic factor identical with leukotriene B?

Eosinophil chemotactic factor (ECF) is a chemotactic factor for eosinophils and neutrophils that is non-peptide in nature. By several lines of evidence, this substance is closely similar or identical to 5,12-di-HETE (leukotriene B). Common denominators induce their derivation from arachidonic acid, their cells of origin, thier physiochemical characteristics and their biological activity. Differences in the ECF activity generated by different types of leukocytes suggest, however, that isomers of leukotriene B or as yet unidentified molecules might be involved. For this reason, ECF should not be called leukotriene B at this point of time.