Neutrophil aggregation--factors modulating stimulus-specific responses.

Abstract

After stimulation with various soluble stimuli, e.g. fMLP and LTB4, human neutrophils aggregated in a characteristic and stimulus-specific way. They formed clumps of cells, mainly pairs and triplets. Their calculated total light-obscuring cell area corresponded well with the recorded aggregation response assessed as light transmittance, when not only neutrophil clumping but also cell swelling and shape changes were taken into account. Changes of neutrophil concentrations had only marginal effects on maximal responses and their kinetics. Lowering cell temperature to 26 degrees C decreased the responses to fMLP, whereas LTB4 responses were more inhibited by increasing temperatures to 42 degrees C. At 26 degrees C, both LTB4 and fMLP induced biphasic aggregation waves with two peaks. Cytochalasin B enhanced the response both to LTB4 and fMLP, and LTB4 responses became biphasic with an early peak preceding the major response. The presence of high concentrations of platelets potentiated aggregation responses, a phenomenon that could not be ascribed to generation of cyclo-oxygenase products. Thus, the formation of neutrophil aggregates and the subsequent change in light transmission can be modulated by several experimental factors which influence the stimulus-specific responses, and the effects on fMLP-induced aggregation under some experimental conditions are different from those on LTB4.