IDENTIFICATION OF PLATELET GLYCOPROTEIN IIB-IIIA AS THE MAJOR BINDING-SITE FOR RELEASED PLATELET-VONWILLEBRAND FACTOR

  • 1 September 1986
    • journal article
    • research article
    • Vol. 68  (3) , 732-736
Abstract
We studied the effect(s) of two monoclonal antibodies, 6D1 and 10E5 (directed against platelet glycoprotein Ib [GPIb] and the GPIIb/IIIa complex, respectively), and purified human plasma fibrinogen on the binding of released platelet-von Willebrand factor (vWf) to the platelet surface. Neither of the monoclonal antibodies nor fibrinogen had any effect on the amount of platelet-vWf expressed on unstimulated platelets or on the amount expressed on platelets stimulated in the absence of extracellular Ca++. However, the antibody directed against GPIIb/IIIa inhibited 72% of the thrombin-induced increase in the platelet-vWf bound to the platelet surface when platelets were stimulated in the presence of 5 mmol/L Ca++. The antibody against GPIb did not inhibit the surface expression of platelet-vWf on stimulated platelets in the presence of Ca++. Purified normal human fibrinogen inhibited the surface binding of platelet-vWf to thrombin-stimulated platelets to a degree similar to that observed with the monoclonal antibody directed against the BPIIb/IIIa complex. These data indicate that platelet-vWf released from platelets binds primarily to the GPIII/IIIa complex at or near the plasma fibrinogen binding site.

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