Von Willebrand factor and platelet adhesiveness

Abstract

A modification of Salzman's method has been used in an attempt to provide an assayin vitrofor the von Willebrand factor. Platelet adhesiveness was increased in von Willebrand's disease by previously coating the beads with normal or haemophilic plasma or cryoprecipitate, whereas von Willebrand plasma had no corrective effect. Antihaemophilic factor (AHF) concentrates were studied in the same way and results compared with experimentsin vivo.

Defective Ristocetin-Induced Platelet Aggregation in von Willebrand's Disease and its Correction by Factor VIII

“…The present study lends further support to the possibility suggested in previous studies that the defect in hemostasis and platelet function in von Willebrand's disease is not owing to an intrinsic platelet defect but rather to a deficiency of a plasma factor necessary for normal platelet function (3,4,7,8). The abnormality of ristocetin-induced platelet aggregation in all patients was corrected by the addition of normal plasma.…”

“…Previous studies indicate that the impaired platelet function in this disorder may not be related to an inherent platelet defect but rather to the deficiency of a plasma factor that is required for normal platelet function. Thus, the abnormal platelet retention can be corrected in vitro by normal plasma (3) or cryoprecipitate (4), and transfusions of these substances may also shorten the bleeding time (4)(5)(6). Recent studies suggest that these corrective effects are associated with the factor VIII molecule.…”

von Willebrand's disease antigen II. A new plasma and platelet antigen deficient in severe von Willebrand's disease.

“…This antigen is not detected in either the platelets or plasma from individuals with severe WD (eight individuals). It is present in all but one of the patients with moderate or variant forms of vWD tested and all normal individuals tested (34 …”

The history of von Willebrand disease

“…Salzman using a method with native blood and rapid flow, demonstrated decreased platelet adhesiveness to glass in vWD [15]. Normal or haemophilic plasma was shown to normalise the reduced platelet adhesiveness as they do the bleeding time in vWD [16]. Jörgensen and Borchgrevink, using electron microscopy, demonstrated a decreased adhesion of platelets to disrupted endothelium in vWD – an observation indicating that the plasma factor lacking in vWD exerted its effect in primary haemostasis via the platelets by enhancing their adhesiveness [17].…”