Neutrophil chemotaxis, phagocytosis, and generation of reactive oxygen species show a hierarchy of responsiveness to increasing concentrations of N-formyl-met-leu-phe

We assessed the effect of varying concentrations of N-formyl-methionyl-leucyl-phenylalanine (fMLP) on neutrophil chemotaxis, phagocytosis, and reactive oxygen species generation. Boyden chamber chemotaxis was first elicited at an fMLP concentration of 10^–11 M, reached a peak at 10^–10M, and declined at higher concentrations. Phagocytosis was first activated at 10^–10M, reached its highest level at 10^–9 M, and declined at higher concentrations. O^–₂, H₂O₂ and OH^• generation were elicited to a significant degree only at a fMLP concentration of 10^–8M, or higher, reaching a peak at 10^–6 M. Thus, a distinct hierarchy was observed in the order of activation of these three neutrophil functions to varying concentrations of a soluble agonist. A teleologic model of neutrophil function that accounts for these observations is proposed.