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(-10) M, and declined at higher concentrations. Phagocytosis was first activated at 10(-10) M, reached its highest level at 10(-9) M, and declined at higher concentrations. O2-, H2O2 and OH. generation were elicited to a significant degree only at a fMLP concentration of 10(-8) M, 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.