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Both TNF and and granulocyte/macrophage CSF (GM-CSF) can activate neutrophils. The aim of this work was to determine the effect of these cytokines on neutrophil degranulation. The secretion of lactoferrin of secondary granules and myeloperoxidase (MPO) of primary granules from single adherent human neutrophils was assayed by use of a reverse hemolytic plaque assay. Both rTNF and rGM-CSF caused secretion of lactoferrin in a dose-dependent manner. Both agents also caused secretion of MPO, but only in the presence of cytochalasin B. Preincubation with pertussis toxin inhibited rGM-CSF-induced secretion of both lactoferrin and MPO. rTNF-induced MPO secretion was also blocked by pertussis toxin, whereas lactoferrin secretion was only slightly affected. Neither rTNF nor rGM-CSF caused any detectable changes in the concentration of cytoplasmic free Ca2+ in fura-2-loaded cells. However, when neutrophils were loaded with increasing concentrations of quin-2 to buffer any local, not detectable, changes in the concentration of cytoplasmic Ca2+, both rTNF- and rGM-CSF-induced secretion of lactoferrin and MPO were almost totally abolished at a relatively low quin-2 concentration. These results suggest a role of a regulatory G-protein and minute local changes in the concentration of cytoplasmic Ca2+ in TNF- and GM-CSF-induced neutrophil degranulation.
Richter et al. (Mon,) studied this question.