Priming of human neutrophil functions by tumor necrosis factor: Enhancement of superoxide anion generation, degranulation, and chemotaxis to chemoattractants C5a and f-Met-Leu-Phe

Recombinant human tumor necrosis factor-α (rTNF) stimulated increased generation of Superoxide anion (O₂^-) by human neutrophils in a concentration-dependent fashion. Preincubation of human neutrophils with rTNF (2.2-2200 units/ml) for 10 min enhanced the subsequent generation of O₂^- in response to C5a and f-MetLeu-Phe(FMLP). Recombinant TNF did not enhance O₂^- generation by neutrophils stimulated with phorbol myristate acetate (PMA). Recombinant TNF alone failed to induce release of myeloperoxidase (MPO) and lysozyme by neutrophils. However, it did enhance the release of MPO and lysozyme by neutrophils stimulated with C5a and FMLP, but not with PMA. Although rTNF alone (0.001-50,000 units/ml) was not chemotactic for neutrophils, preincubation of neutrophils with rTNF (0.001-0.1 units/ml) enhanced the chemotactic activity of suboptimal concentrations of C5a (0.1 nM) and FMLP (5 nM). Neutrophils treated with high concentrations of rTNF (100-10,000 units/ml) showed inhibition of random movement and of chemotaxis induced by C5a or FMLP. We conclude from these studies that rTNF primes neutrophils for enhanced responses to subsequent stimuli and thus may augment the inflammatory response by increased oxidant production and lysosomal enzyme release and promote down-regulation of chemotactic movement.