Enhanced prothrombin-converting activity and factor Xa binding of platelets activated by the alternative complement pathway.

Platelet prothrombin-converting activity and factor Xa binding were studied after exposure of human platelet rich plasma (PRP) to various conditions leading to platelet activation. Zymosan resulted in increased platelet-bound C3, enhanced prothrombin-converting activity and increased factor Xa binding. Similar findings were observed with normal platelets resuspended in factor XII-deficient plasma.