Degranulation of primary and secondary granules in adherent human neutrophils

The aim of this study was to investigate whether neutrophil adhesion to extracellular matrix proteins like fibronectin, fibrinogen, and albumin influence the release proteins from primary and secondary granules of neutrophils stimulated by phorbol-myristate-acetate (PMA) and formyl-methionyl-leucyl-phenylalanine (f-MLP). Isolated granulocytes plated on wells coated with fibronectin, fibrinogen, and albumin were stimulated with f-MLP (10-7 mol/l), PMA (10-9 mol/l), Mn2+ (5 mmol/l), or combinations of these stimuli, and the degree of adhesion to protein-coated surfaces and the amount of granule proteins released was quantified during 90 min of incubation. PMA, in combination with Mn2+, induced a maximum release of approximately 80% of the intracellular content of lactoferrin and human neutrophil lipocalin (HNL) and 15-20% of the myeloperoxidase (MPO) content regardless of the protein used. PMA or f-MLP alone induced 30-40% release of lactoferrin and HNL depending on the protein that the cells were plated on. Adhesion and release of lactoferrin and HNL were quantitatively related when induced by PMA and PMA plus Mn2+, but not by f-MLP. The mean release of lactoferrin and HNL showed a significant negative relationship to the viability of the cells. In conclusion, adhesion modulates neutrophil degranulation, but it is not always quantitatively related or related in time.