Effect of tumor necrosis factor on granule release and LTB4 production in adherent human polymorphonuclear leukocytes

Abstract

Tumor necrosis factor (rTNF) has previously been shown to induce PMN chemotaxis, stimulate PMN adhesion to vascular endothelium and stimulate hydrogen peroxide secretion from PMNs adhered to biological surfaces. We investigated the activity of both rTNF alpha and rTNF beta on adherent and suspension cultures of human PMNs. rTNF alpha selectively stimulated the release of the specific granule in a dose dependent manner. Exocytosis of the specific granule was measured with an enzyme-immunoassay for lactoferrin and a radioassay for vitamin B12-binding protein. Adherent PMNs released up to 60% of the total lactoferrin content of the cells with no increase in myeloperoxidase (MPO) secretion when stimulated with 0.1-10 nM rTNF alpha. The PMNs in suspension cultures also selectively released the specific granule, although total release was reduced suggesting that adherence of PMNs increased their ability to respond to physiological stimuli. When PMNs in suspension cultures or adherent cells were stimulated with rTNF alpha, no LTB4 production was detectable, yet the cells retained the ability to synthesize LTB4 when stimulated with calcium ionophore A23187. Neither rTNF alpha or rTNF beta stimulated the release of the azurophilic granule, measured by the secretion of MPO and neutrophil elastase activity. These results suggest that a function of rTNF alpha and rTNF beta on PMNs is the release of the contents within the specific granule.