The lipooxygenase pathway product of arachadinoic acid leucotriene-B4 (LTB4), is released by activated leucocytes, it is a potent chemoattractant and induces ahesion and trans migration in venules.
Tumor necrosis factor- (TNF-) is one of the most pro-inflammatory cytokines known. It is produces by the activated leucocyte.
Elastase, collagenase and gelatinase are released, these play a role in making a hole in the basement membrane to permit transmigration of leucocytes. They also function to degrade the interstitial matrix.