ACTIVATION OF HUMAN NEUTROPHILS BY C3A AND C5A COMPARISON OF THE EFFECTS ON SHAPE CHANGES, CHEMOTAXIS, SECRETION, AND RESPIRATORY BURST

The effects of anaphylatoxin C3a on human neutrophils were studied in comparison with C5a. Both peptides induced a transient shape change re sponse and a respiratory burst. In both cases C3a was 50- to 100-times less potent than C5a. A marked chemotactic response with bimodal conc entration dependence was obtained with C5a, but no neutrophil chemotax is was observed with C3a. Repeated stimulation led to homologous desen sitization of shape changes and respiratory burst but no cross-desensi tization, indicating that the two anaphylatoxins act through separate receptors. The lack of chemotactic activity suggests that C3a is not i nvolved in neutrophil recruitment into infected or inflamed tissues.