Effect of neutrophil adhesion on the size of aggregates formed by agonist-activated platelets

In this study we have investigated the effect of human neutrophil on agonist-induced platelet aggregation by using the laser-light scattering method that can detect a two-phase process, formation of small aggregates followed by large aggregate formation. When nonstimulated neutrophils were added to agonist-stimulated platelet-rich plasma (PRP), the large platelet aggregates were decreased and the small ones were increased by using either collagen, thrombin or ADP as agonist. Scanning-electron microscopic observation showed marked adhesion of neutrophil to aggregated platelets. The supernatant from neutrophils cell lysate (neutrophil supernatant) showed inhibitory effect similar to that with intact neutrophils, suggesting that the inhibitory effect by neutrophils was due to soluble component(s) including proteases released from neutrophils adhered to activated platelets. We have examined the effect of inhibition of a major released protease, elastase. The addition of its potent inhibitor elafin to intact n...