New approach to determination of specific functions of platelet membrane sites

Abstract

IT has been suggested that the layer of bound carbohydrate on the surface of a platelet contains groupings vital to the haemostatic function of the platelet¹. This haemostatic role is largely dependent on the ability of the platelet to adhere to exposed subendothelial components in the event of vessel damage². Platelet aggregation, induced by bovine factor VIII and ristocetin, and platelet adhesion to subendothelium are impaired in the Bernard–Soulier syndrome, while aggregation induced by ADP is apparently normal^3,4. A gross abnormality in the 155,000-molecular weight glycoprotein seen in membrane fractions prepared from platelets from this syndrome⁵ suggests that the glycoprotein acts as an acceptor–receptor during the interation with subendothelium and macromolecular aggregation-inducing agents. Here we report further evidence that a specific site on the platelet is required for ristocetin and bovine factor VIII to induce platelet aggregation and for platelet adhesion when aggregation and platelet adhesion to subendothelium are inhibited by an acquired antiplatelet antibody found in a polytransfused Bernard–Soulier patient. This antibody induced in vitro, on normal human platelets, a specific Bernard–Soulier-like defect, so that adhesion to subendothelium was impaired and aggregation with ristocetin and bovine factor VIII was defective, while ADP-mediated aggregation was unaffected.