scholarly journals Effect of multimeric structure of the factor VIII/von Willebrand factor protein on binding to platelets

Blood ◽  
1981 ◽  
Vol 58 (2) ◽  
pp. 387-397 ◽  
Author(s):  
HR Gralnick ◽  
SB Williams ◽  
DK Morisato
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Competitive Inhibition ◽  
Human Platelets ◽  
Factor Vii ◽  
Variant Form ◽  
Factor Binding ◽  
Plasma Factor ◽  
Von Willebrand ◽  
Willebrand Factor

The characteristics of the intact factor VIII/von Willebrand factor protein binding to human platelets was compared to 2-mercaptoethanol- treated factor VIII/von Willebrand factor protein and to fractions of plasma factor VIII/von Willebrand factor protein that elute after the void volume. These studies indicate that the factor VIII/von Willebrand factor protein larger size oligomers bind preferentially with high affinity to low capacity sites on human platelets. The intermediate and smaller size oligomers bind with intermediate or low affinity to sites with a much greater capacity. The results from binding analysis are also paralleled by the competitive inhibition of the intact factor VIII/von Willebrand factor protein by the various 2-mercaptoethanol- treated materials. These studies indicate that the two classes of binding sites seen in previous reports of factor VII/von Willebrand factor binding reflect heterogeneity in the oligomer size of the factor VIII/von Willebrand factor protein used in these assays. This study provides a model for understanding some of the normal structure- function relationships of the normal factor VIII/von Willebrand factor protein and the defect(s) in a variant form of von Willebrand's disease. In this form of the disease, decreased factor VIII/von Willebrand factor binding to platelets is reflected in decreased von Willebrand factor activity but coagulant and/or antigen levels are normal or only slightly decreased.

scholarly journals Effect of multimeric structure of the factor VIII/von Willebrand factor protein on binding to platelets

Blood ◽  
1981 ◽  
Vol 58 (2) ◽  
pp. 387-397 ◽  
Author(s):  
HR Gralnick ◽  
SB Williams ◽  
DK Morisato
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Competitive Inhibition ◽  
Human Platelets ◽  
Factor Vii ◽  
Variant Form ◽  
Factor Binding ◽  
Plasma Factor ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract The characteristics of the intact factor VIII/von Willebrand factor protein binding to human platelets was compared to 2-mercaptoethanol- treated factor VIII/von Willebrand factor protein and to fractions of plasma factor VIII/von Willebrand factor protein that elute after the void volume. These studies indicate that the factor VIII/von Willebrand factor protein larger size oligomers bind preferentially with high affinity to low capacity sites on human platelets. The intermediate and smaller size oligomers bind with intermediate or low affinity to sites with a much greater capacity. The results from binding analysis are also paralleled by the competitive inhibition of the intact factor VIII/von Willebrand factor protein by the various 2-mercaptoethanol- treated materials. These studies indicate that the two classes of binding sites seen in previous reports of factor VII/von Willebrand factor binding reflect heterogeneity in the oligomer size of the factor VIII/von Willebrand factor protein used in these assays. This study provides a model for understanding some of the normal structure- function relationships of the normal factor VIII/von Willebrand factor protein and the defect(s) in a variant form of von Willebrand's disease. In this form of the disease, decreased factor VIII/von Willebrand factor binding to platelets is reflected in decreased von Willebrand factor activity but coagulant and/or antigen levels are normal or only slightly decreased.

scholarly journals Subcellular platelet factor VIII antigen and von Willebrand factor.

1975 ◽  
Vol 141 (5) ◽  
pp. 1101-1113 ◽  
Author(s):  
R L Nachman ◽  
E A Jaffe
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Human Platelets ◽  
Factor Vii ◽  
Platelet Factor ◽  
Plasma Factor ◽  
Factor Viii Antigen ◽  
Von Willebrand ◽  
Willebrand Factor

Subcellular membrane and granule fractions derived from human platelets contain factor VIIII antigen and von Willebrand factor activity but not factor VII procoagulant activity. Circulating platelets constitute a significant reservoir of plasma factor VIII antigen, containing approximately 15% of the amount of factor VIII antigen present in platelet-poor plasma. The antibiotic ristocetin, which aggregates human platelets in the presence of von Willebrand factor, nonspecifically precipitates platelet membrane factor VIII antigen. Thus normal platelets contain surface-bound as well as internally stored von Willebrand factor, a protein synthesized by endothelial cells which is necessary for normal platelet function in vivo.

Effect Of The Multimeric Structure Of The Factor VIII/Von Willebrand Factor Protein On Binding To Human Platelets

1981 ◽  
Author(s):  
H Gralnick ◽  
S Williams ◽  
D J Morisato
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Competitive Inhibition ◽  
High Capacity ◽  
Molecular Size ◽  
Human Platelets ◽  
Affinity Binding ◽  
Platelet Receptor ◽  
Von Willebrand ◽  
Willebrand Factor

We have studied the characteristics of binding of intact factor VIII/von Willebrand factor (f. VIII/vWf) protein and 2-mercaptoethanol (2ME) treated f. VIII/vWf protein to human platelets. The purified f. VIII/vWf was radiolabelled with tritiated 3H potassium borohydride; 4.5 × 103 molecules of the intact radiolabelled material bound per platelet. Of these some molecules bound with a high affinity/low capacity (Kd 0.21 nM and 1.5 × 103 molecules) and another with a low affinity/high capacity (Kd 2.5 nM and 3 × 103 molecules). When the material was reduced with 2ME at 0.01%, it bound with an intermediate affinity of 1.6 nM with a capacity of 4.0 × 103 and a low affinity binding of 12.5 nM and a capacity of 4.0 × 103 . The 0.1% 2ME-treated material revealed only low affinity binding with a Kd of 15 nM and the number of molecules bound 13 × 103. Studies of competitive inhibition of the intact f. VIII/vWf binding to human platelets by the reduced materials revealed that the smallest f. VIII/vWf protein (i.e., 0.1% 2ME) was the least effective while the 0.01% 2ME material was intermediate between the 0.1% and the intact material. The differences noted in the ability to displace the intact material as well as in binding to the human platelet were paralleled by decreases in the vWf activity of these proteins.These studies aid in our understanding of the binding of the f. VIII/vWf to platelets in that the binding sites on platelets may be homogeneous while the ligand is heterogenous. These studies reinforce the structure/function relationships of f. VIII/vWf proteins which have been defined using ristocetin-induced platelet aggregation (i.e., the minimum molecular size of the f. VIII/vWf protein and the penultimate galactose residues on the carbohydrate side chain). We conclude that these defects of the f. VIII/vWf protein also interfere with the protein binding to its platelet receptor and that f. VIII/vWf binding to platelets is an important primary step in hemostasis.

scholarly journals Precipitating antibodies to factor VIII/von Willebrand factor in von Willebrand's disease: effects on replacement therapy

Blood ◽  
1981 ◽  
Vol 57 (1) ◽  
pp. 25-31 ◽  
Author(s):  
PM Mannucci ◽  
ZM Ruggeri ◽  
N Ciavarella ◽  
MD Kazatchkine ◽  
JF Mowbray
Keyword(s):  
Factor Viii ◽  
Replacement Therapy ◽  
Antibody Titer ◽  
Von Willebrand Factor ◽  
Factor Vii ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
Plasma Factor ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Precipitating antibodies to factor VII/von Willebrand factor can develop in patients with severe homozygous-like von Willebrand's disease following multiple transfusions with blood derivatives. This study of 4 patients treated with cryoprecipitate for 13 different bleeding episodes demonstrates that the occurrence of such antibodies interferes with the management of the disease. The control of mucosal bleeding was poor, whereas more favorable responses were obtained in soft-tissue hemorrhages. These findings probably relate to failure of replacement therapy to shorten the prolonged bleeding time. Immediately after treatment, measurement of plasma factor VIII/von Willebrand factor-related antigen and ristocetin cofactor showed either no increase, or very low values, depending on the pre-infusion antibody titer. Levels of the factor VIII/von Willebrand factor-related procoagulant activity in the circulation were also lower than predicted and usually there was no evidence of the delayed and sustained rise typically observed in uncomplicated von Willebrand's disease. An anamnestic rise in antibody titer appeared 6–15 days after treatment and showed no obvious relationship with the amount of cryoprecipitate infused. Replacement therapy invariably caused severe side effects during, or immediately after, concentrate infusion. The results of in vitro studies support the view that these reactions were due to the appearance of circulating immune complexes.

scholarly journals Precipitating antibodies to factor VIII/von Willebrand factor in von Willebrand's disease: effects on replacement therapy

Blood ◽  
1981 ◽  
Vol 57 (1) ◽  
pp. 25-31
Author(s):  
PM Mannucci ◽  
ZM Ruggeri ◽  
N Ciavarella ◽  
MD Kazatchkine ◽  
JF Mowbray
Keyword(s):  
Factor Viii ◽  
Replacement Therapy ◽  
Antibody Titer ◽  
Von Willebrand Factor ◽  
Factor Vii ◽  
Von Willebrand's Disease ◽  
Von Willebrand’S Disease ◽  
Plasma Factor ◽  
Von Willebrand ◽  
Willebrand Factor

Precipitating antibodies to factor VII/von Willebrand factor can develop in patients with severe homozygous-like von Willebrand's disease following multiple transfusions with blood derivatives. This study of 4 patients treated with cryoprecipitate for 13 different bleeding episodes demonstrates that the occurrence of such antibodies interferes with the management of the disease. The control of mucosal bleeding was poor, whereas more favorable responses were obtained in soft-tissue hemorrhages. These findings probably relate to failure of replacement therapy to shorten the prolonged bleeding time. Immediately after treatment, measurement of plasma factor VIII/von Willebrand factor-related antigen and ristocetin cofactor showed either no increase, or very low values, depending on the pre-infusion antibody titer. Levels of the factor VIII/von Willebrand factor-related procoagulant activity in the circulation were also lower than predicted and usually there was no evidence of the delayed and sustained rise typically observed in uncomplicated von Willebrand's disease. An anamnestic rise in antibody titer appeared 6–15 days after treatment and showed no obvious relationship with the amount of cryoprecipitate infused. Replacement therapy invariably caused severe side effects during, or immediately after, concentrate infusion. The results of in vitro studies support the view that these reactions were due to the appearance of circulating immune complexes.

Interactions of Purified Rat Factor VIII/von Willebrand Factor with Rat and Human Platelets – Effect of Albumin and Ristocetin

1984 ◽  
Vol 52 (01) ◽  
pp. 057-059 ◽  
Author(s):  
E Dejana ◽  
M Furlan ◽  
B Barbieri ◽  
M B Donati ◽  
E A Beck
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Rat Plasma ◽  
Human Platelets ◽  
High Concentrations ◽  
Low Sensitivity ◽  
Von Willebrand ◽  
Induced Aggregation ◽  
Willebrand Factor ◽  
Rat Platelets

SummaryRat platelets do not respond to ristocetin in their own plasma nor do they aggregate in the presence of bovine or porcine factor VIII von Willebrand factor (F VIII R:WF) or human F VIII R:WF in presence of ristocetin. However, rat plasma supports ristocetin induced aggregation of washed human platelets. In this study we report on purification of rat F VIII R:WF from cryoprecipitate. Similarly to porcine or bovine material, purified rat F VIII R:WF induced aggregation of human washed fixed platelets. This effect was enhanced by addition of ristocetin and was not modified by addition of albumin. Rat washed platelets were aggregated by ristocetin in the presence of rat or human F VIII R:WF provided that high concentrations of ristocetin are added in a system essentially free of extraneous proteins. Increasing concentrations of albumin dramatically reduced the ability of ristocetin to aggregate rat platelets while human platelet aggregation by human or rat F VIII R:WF was only moderately affected.These studies show that rat F VIII R:WF can interact with rat and human platelets. The lack of response of rat platelets to ristocetin in their own plasma is most likely due to a low sensitivity of rat platelets to this drug and to an inhibitory activity of plasma proteins on this reaction.

scholarly journals Factor VIII/von Willebrand factor in subendothelium mediates platelet adhesion

Blood ◽  
1985 ◽  
Vol 65 (4) ◽  
pp. 823-831 ◽  
Author(s):  
VT Turitto ◽  
HJ Weiss ◽  
TS Zimmerman ◽  
II Sussman
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Vessel Wall ◽  
Platelet Adhesion ◽  
Human Factor ◽  
Rabbit Aorta ◽  
Human Factor Viii ◽  
Plasma Factor ◽  
Von Willebrand ◽  
Willebrand Factor

The present studies were undertaken to determine whether factor VIII/von Willebrand factor (vWF) present in the vessel wall (in addition to that in plasma) may mediate the attachment of platelets to subendothelium. Subendothelium from everted rabbit aorta was exposed to human citrated blood flowing through an annular perfusion chamber at 40 mL/min (wall shear rate of 2,600 s-1 for five minutes). The vessel segments were incubated at 37 degrees C for one hour with various dilutions of either goat-anti-rabbit factor VIII/vWF serum or an IgG fraction prepared from the serum. Control segments were incubated with serum or IgG from a nonimmunized goat. Values of platelet contact (C), platelet adhesion (C + S), and thrombus formation (T) on the subendothelium were evaluated by a morphometric technique. Compared with vessels incubated with fractions prepared from a normal goat, a significant decrease in platelet adhesion (C + S), ranging from 45% to 65%, was observed on vessels incubated with various dilutions (1:5 to 1:50) of either serum or IgG fractions of goat-anti-rabbit factor VIII/vWF. A similar decrease in platelet adhesion was observed with vessels incubated with an F(ab')2 fragment against rabbit factor VIII/vWF prepared in the goat. When goat-anti-rabbit factor VIII/vWF IgG was added to rabbit blood (1:75 dilution), platelet adhesion was reduced to the same extent (65%) on normal rabbit vessels and on vessels pre-incubated with goat-anti-rabbit factor VIII/vWF. Immunofluorescence studies revealed the presence of rabbit factor VIII/vWF in the subendothelium of rabbit aorta and the continued binding of the goat-anti-factor VIII/vWF antibodies on subendothelium during the perfusion studies. No uptake of human factor VIII/vWF on the rabbit subendothelium was observed by this immunologic technique; human factor VIII/vWF was found to be entirely associated with the attached human platelets. Thus, factor VIII/vWF in the vessel wall may mediate platelet attachment to subendothelium in a manner similar to that of plasma factor VIII/vWF.

The Importance of the Carbohydrate Moiety of the Factor VIII/Von Willebrand Factor Protein in Binding to and Causing Agglutination of Human Platelets

1979 ◽  
Author(s):  
H.R. Gralnick ◽  
D.K. Morisato
Keyword(s):  
Factor Viii ◽  
Von Willebrand Factor ◽  
Binding Sites ◽  
Human Platelets ◽  
Galactose Oxidase ◽  
Scatchard Analysis ◽  
Human Fibrinogen ◽  
Number Of Binding Sites ◽  
Von Willebrand ◽  
Willebrand Factor

We have investigated the binding of radiolabelled factor VIII/von Willebrand factor (f. VIII/vWf) protein to human platelets (P) in the presence of ristocetin (R). In these atudies we have delineated the importance of the carbohydrate (CHO) moiety(s) in both the binding to the P and in cauaing agglutination of P. Binding of the f.VIII/vWf protein to human P was time and temperature dependent and dependent on the concentration of R. Binding was specific in that it could not be blocked by human fibrinogen but was inhibited by unlabelled f.VIII/vWf protein. In studies utilizing varying amounts of the f.VIII/vWf protein or by varying the number of P in the assay, the number of binding sites for the f. VIII/vWf protein were estimated at 9,500-9,800 per platelet. Scatchard analysis revealed 11,000 binding sites with 3,600 of high affinity and 7,400 of low affinity. Removal of the sialic acid of the f.VIII/vWf protein resulted in no significa nt change in its ability to bind to the P surface or cause agglutination in the presence, IR. Removal of the galactose by 6-galactosijase resulted in a 75% reduction of binding of the f.VIII/vWf protein and a 91% decrease in the agglutination of human P. Similar studies with galactose oxidase showed that oxidation of the penultimate galactose residue s results in a decrease in agglutination comparable to that seen with 6-galactosidase treatment. These studies indicate that the CHO moiety of the f.VIII/vWf protein is important in both binding to the P surface as well as causing agglutination of human P.

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