Neutrophil chemotaxis in response to surface-bound C5a

Abstract

Many biological functions of neutrophils can be initiated by surface-bound stimuli. This report describes experiments examining the role of surface-bound C5a on neutrophil chemotaxis. Cellulose-nitrate filters were preincubated with various concentrations of highly purified human C5a. After washing the filters, incubating for an additional hour and washing again, the filters were used in a standard two-filter chemotaxis assay with human neutrophils and no additional stimulus. The bound C5a induced an effective directional migration of the neutrophils. Establishment of a chemotactic gradient within the filters was suggested by the absence of directional migration when the pretreated C5a filters were inverted before the chemotactic assay. The presence of the chemotactic gradient was further shown by use of autoradiography and 125I-C5a. These studies suggest that interaction of neutrophils with surface-bound C5a can promote the movement of the neutrophil in the direction of increased concentrations of the bound ligand.