Studies of the human factor VIII/von Willebrand factor protein. III. Qualitative defects in von Willebrand's disease.

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We have investigated and characterized the abnormalities in four unrelated patients with von Willebrand's disease (vWd) who have (a) enhanced ristocetin-induced platelet aggregation (RIPA) at low ristocetin concentrations, (b) absence of the largest plasma von Willebrand factor (vWf) multimers, and (c) thrombocytopenia. The platelet-rich plasma of these patients aggregates spontaneously without the addition of any agonists. When isolated normal platelets are resuspended in patient plasma spontaneous aggregation occurs; however, the patients' plasmas did not induce platelet aggregation of normal washed formalinized platelets. When the patients' platelets are suspended in normal plasma, spontaneous aggregation is not observed. The spontaneous platelet aggregation (SPA) is associated with dense granule secretion as measured by ATP release and alpha granule release as measured by fl-thromboglobulin and platelet factor 4 release.The SPA is totally inhibited by 5 mM EDTA, prostaglandin I2, and dibutryl cyclic AMP, while it is only partially inhibited by 1 mM EDTA, acetylsalicylic acid, or apyrase. A monoclonal antibody directed against glycoprotein Ib (GPIb) and/or a monoclonal antibody against the glycoprotein IIb/IIIa (GPIIb/ IIIa) complex totally inhibits the SPA.The vWf was isolated from the plasma of one of these patients. The purified vWf induced platelet aggregation of normal platelets resuspended in either normal or severe vWd plasma, but the vWf did not induce platelet aggregation of normal platelets resuspended in afibrinognemic plasma. Sialic acid and galactose quantification ofthe patient's vWf revealed approximately a 50% reduction compared with normal vWf. These studies indicate that a form of vWd exists, which is characterized by SPA that is induced by the abnormal plasma vWf. The SPA is dependent on the presence of plasma fibrinogen, and the availability of the GPIb and the GPIIb/IIIa complex. In this variant form of vWd the abnormal vWf causes enhanced RIPA, SPA, and thrombocytopenia.

“…blood, and purification of normal and patient F.VIII/vWf protein were performed as previously described (12,13). Cryoprecipitate was prepared from 240 ml of fresh frozen plasma.…”

Section: Methodsmentioning

confidence: 99%

Von Willebrand's disease with spontaneous platelet aggregation induced by an abnormal plasma von Willebrand factor.

Grainick¹,

Williams²,

McKeown³

et al. 1985

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“…Abbreviations used in this paper: EACA, E-amino caproic acid; endo F, endo-,-N-acetyl-glucosaminidase F; TBS, Tris-buffered saline; vWF, von Willebrand factor; eF-vWF, vWF modified by endo F; neu-vWF, vWF modified by neuraminidase; neu-#-gal-vWF, vWF modified by neuraminidase and ,B-galactosidase sequentially; ef-neu-vWF, vWF modified by endo F and neuraminidase sequentially; eF-neu-#-gal-The largest vWF multimers appear to be the most hemostatically effective and are absent in some variants of von Willebrand disease (1)(2)(3)(4). Carbohydrate composes 10-15% of the mass of vWF and has been implicated in the structural and functional integrity of the molecule (1).…”

Section: Introductionmentioning

confidence: 99%

Carbohydrate moiety of von Willebrand factor is not necessary for maintaining multimeric structure and ristocetin cofactor activity but protects from proteolytic degradation.

Federici¹,

Elder²,

Marco³

et al. 1984

“…The precursor protein is proteolytically processed to yield two distinct proteins, i.e., vW AgIl and the mature vWF subunit (1 1-13). The availability of vWF-cDNA probes has led to the identification of three restriction fragment length polymorphisms (RFLPs) (14)(15)(16) (21) and the vWFRco activity was measured using formalin-fixed platelets as described (22 by "nick translation," were done as described (27, 28). The filters were washed at a stringency of0.3X SSC, 0.1% SDS at 65°C and autoradiography was performed.…”

Section: Introductionmentioning

confidence: 99%

Genetic linkage of two intragenic restriction fragment length polymorphisms with von Willebrand's disease type IIA. Evidence for a defect in the von Willebrand factor gene.

Verweij¹,

Quadt²,

Briët³

et al. 1988

Restriction fragment length polymorphisms (RFLPs), using the enzymes Bgl II and Xba I in conjunction with human von Willebrand factor (vWF) cDNA probes, have been described previously. In the present study we demonstrate the localization of both genetic markers within the vWF gene. The RFLPs were used to study the segregation of alleles associated with von Willebrand's disease (vWD) type IIA in a comprehensive, affected family. Individuals of this family were tested for their bleeding time and their plasma was analyzed for vWF antigen concentration and vWF ristocetin-cofactor activity. Based on these data, the affected members were diagnosed as vWD type-IIA patients; this conclusion was confirmed by the analysis of the multimeric vWF pattern of some of the patients. It was demonstrated that both RFLPs are completely linked with the vWD type-IIA trait. From this finding, we conclude that the defect that causes the vWD type IIA is most likely due to a mutation in the vWF gene and not to a mutation in a gene involved in posttranslational processing of the vWF protein.