Plasma Co-factors in Adenosine Diphosphate-induced Aggregation of Human Platelets

Abstract

THE aggregation of washed human platelets in vitro by adenosine diphosphate (ADP) requires calcium and is stimulated by the addition of platelet-free plasma¹. The identity of the plasma activity has been the subject of recent conflicting reports. Hellem and Owren² have suggested that the plasma factor is that entity missing in von Willebrand's disease; but others^3,4 have found that ADP-induced platelet aggregation proceeds normally in plasma from patients with established von Willebrand's disease. McLean et al.⁵ and Cross⁴ have indicated that fibrinogen may be the plasma co-factor, and Caen⁶ has recently suggested that both fibrinogen and the anti-von Willebrand factor participate in ADP-induced platelet aggregation.