Search

Circulating thrombomodulin is a novel endothelial cell marker, which may reflect the endothelial injury. Plasma levels of thrombomodulin were quantitated by an enzyme-linked immunosorbent assay (ELISA) in patients with hematological malignancies, liver disease, diabetes mellitus, collagen disease, thrombotic disease, and disseminated intravascular coagulation (DIC), and the thrombomodulin values were compared with those of von Willebrand factor antigen (vWf:Ag) and tissue-type plasminogen activator (t-PA) which are released from stimulated or damaged endothelial cells. The mean plasma concentrations of thrombomodulin in these disease states were elevated as compared with healthy subjects. A relatively high mean thrombomodulin level was observed in DIC, liver disease, and collagen disease. Abnormally high thrombomodulin values (greater than normal mean value + 3 SD) were found in 32.3% of patients with hematological malignancies, 57.7% of patients with liver disease, 39.3% of patients with diabetes mellitus, 30.0% of patients with collagen disease, 23.1% of patients with thrombotic disease, and 69.0% of patients with DIC. Plasma concentrations of both vWf:Ag and t-PA were also elevated in these patients. On the whole, the plasma thrombomodulin concentration was positively correlated with vWf:Ag (r = 0.441, P less than 0.001) and t-PA (r = 0.398, P less than 0.001). These findings indicate that the elevation of plasma thrombomodulin is frequently seen in a variety of diseases and circulating thrombomodulin is possibly useful for evaluating the endothelial damage in selected disease states.

A fast-migrating precipitin peak which showed a reaction of partial immunochemical identity with the major von Willebrand factor (vWf) component was detected by crossed immunoelectrophoresis in agarose gel in plasma but not in platelets from a patient with type IIA von Willebrand's disease (vWD). Another patient undergoing urokinase therapy had a vWf fragment in plasma which was antigenically cross-reactive with the major vWf component. When plasma from both patients was mixed and electrophoresed together in the first dimension, two fast-moving precipitin arcs were demonstrated in the second dimension. These data indicate that two different kinds of vWf fragments can be generated in vivo.

We studied the multimeric composition of plasma von Willebrand factor (vWf) in 26 patients with chronic myelocytic leukaemia (CML); 13 in chronic phase, 8 in blast crisis, 5 in both chronic phase and blast crisis. The relative amount of large (multimer band greater than or equal to 11) multimers calculated by densitometer scan following SDS-agarose gel electrophoresis was 14.6 +/- 2.9% (mean +/- SD) in normal controls, 8.7 +/- 4.7% in chronic phase and 15.0 +/- 5.2% in blast crisis. CML patients in chronic phase (but not in blast crisis) had a significantly lower percentage of large multimers than normal controls (p less than 0.001). The relative amount of large multimers was positively correlated with a ratio of ristocetin cofactor/vWf antigen (p less than 0.005), and was negatively correlated with platelet count (p less than 0.001), WBC count (p less than 0.05) and granulocyte count (p less than 0.05). We conclude that some patients with CML, especially in chronic phase, lack large multimers. The negative correlation of the relative amount of large multimers with platelet and granulocyte count suggests that large multimers may be consumed in high platelet count states or degraded by protease(s) from increased blood cells.

Platelet-type von Willebrand's disease (vWD) is a bleeding disorder characterized by a heightened interaction between platelets and von Willebrand factor (vWF) as the result of an intrinsic platelet abnormality (probably in GPIb). Platelet aggregability was nearly normal in response to thrombin, wheat germ agglutinin and Ricinus communis agglutinin in this disorder. Unmodified platelets showed no aggregation upon the addition of peanut agglutinin. Partially purified human vWF induced little aggregation of washed patient platelets, but the aggregation was greatly enhanced in the presence of plasma devoid of vWF. Monoclonal antibodies directed against GPIb and GPIIb/IIIa as well as EDTA completely inhibited vWF-induced aggregation. These results indicate that human vWF induces aggregation of platelet-type vWD platelets in the presence of divalent cations and some plasma cofactor(s), and that both GPIb and GPIIb/IIIa are involved in this aggregation.

The profile of blood coagulation and fibrinolysis was studied in detail in eight patients with acute thrombotic thrombocytopenic purpura (TTP). In the majority of the patients, fibrinogen, factor XIII, antithrombin III, alpha 2-plasmin inhibitor, plasminogen, and alpha 2-macroglobulin were normal, whereas FDP, plasmin-alpha 2-plasmin inhibitor complex, and tissue-type plasminogen activator antigen were marginally or moderately elevated. Low fibronectin values were observed in four patients. Protein C and C4b-binding protein were nearly normal, whereas total protein S and free protein S were reduced in five and six patients, respectively. A positive correlation was found between total protein S and C4 and between free protein S and C3. von Willebrand factor antigen (vWf:Ag) and ristocetin cofactor (RCof) were either normal or elevated, but RCof/vWf:Ag ratio was decreased in seven patients. Crossed immunoelectrophoresis and sodium dodecyl sulfate (SDS)-agarose gel electrophoresis revealed that the large vWf multimers were either absent from or relatively decreased in all patients except one. In addition, one patient had unusually large vWf multimers, and a low-molecular-weight vWf fragment was apparently observed in three patients. These findings indicate that the intravascular generation of thrombin and plasmin was minimal in TTP and suggest that the alterations of the vWf molecule were caused not only by consumption through its participation in platelet thrombus formation but also by accelerated proteolysis. Low protein S values would be related to the immunological abnormalities underlying TTP.

Blood platelets from patients with platelet-type von Willebrand disease (vWD) aggregate upon the addition of human von Willebrand factor (vWf) in the absence of ristocetin or other stimulating factors. We measured quantitatively the ability of vWf to induce directly aggregation of platelet-type vWD platelets (platelet-type vWD platelet aggregating factor [PT-PAF]). Cryoprecipitate and factor VIII concentrates were used as a source of vWf of various multimeric composition. The PT-PAF activity was dependent on the multimer size of vWf, like in the case of ristocetin cofactor (RCof) activity. However, PT-PAF activity was not equivalent to RCof activity and the relative PT-PAF/RCof ratio ranged from 1.00 to 0.18 in the materials studied. The preparations containing the higher-molecular-weight multimers had higher PT-PAF/RCof ratio. These findings suggest that PT-PAF activity is a functional expression of more highly polymerized multimers of vWf as compared with RCof activity. Measurement of PT-PAF would serve as a novel functional assay of vWf.

We performed a hemostatic evaluation in detail in a patient with suspected amyloidosis who was suffering from several bleeding episodes. He had a shortened euglobulin clot lysis time, decreased alpha 2-plasmin inhibitor (alpha 2-PI), decreased plasminogen, elevated tissue-type plasminogen activator (t-PA), elevated plasmin-alpha 2-PI complex, and decreased ratio of ristocetin cofactor to von Willebrand factor (vWF) antigen. Fibrinogen and fibrin/fibrinogen degradation products levels fluctuated, with abnormal values on several occasions. On crossed immunoelectrophoresis, plasmin-alpha 2-PI complex and vWF fragment were demonstrated in the patient plasma. These abnormal findings and bleeding symptoms improved following the administration of tranexamic acid. Discontinuation of tranexamic acid resulted in deterioration of these parameters. These observations indicate that pathologic fibrinolysis (continuous intravascular plasmin generation) characterized by the consumption of alpha 2-PI and plasminogen, formation of plasmin-alpha 2-PI complex, and fragmentation of vWF contributed to the bleeding in this patient. It is important to recognize excessive fibrinolysis as the underlying cause of bleeding in these patients, since specific treatment with antifibrinolytic agents is effective in controlling the bleeding.

Platelet-type von Willebrand's disease (VWD) is a recently described bleeding disorder characterized by a heightened interaction between platelets and von Willebrand factor (vWF) as the result of an intrinsic platelet-membrane abnormality. Administration of cryoprecipitate into a patient with this disorder was followed by thrombocytopenia in vivo and "spontaneous" platelet aggregation in vitro. However, a prolonged bleeding time was shortened and sufficient haemostasis was achieved without thromboembolic complications. These results provide evidence that human vWF infused with cryoprecipitate directly interacts with platelet-type vWD platelets, causing thrombocytopenia in vivo, and suggest that impaired primary haemostasis is related to the depletion of the high-molecular-weight vWF multimers in the circulating plasma.

Cryoprecipitate has proved to correct the hemostatic defects in von Willebrand's disease (vWD) and platelet-type vWD. However, recent studies have revealed that transmission of the AIDS retrovirus (HIV) occurs through exposure to blood products including cryoprecipitate. Treatment with heat-treated factor VIII/von Willebrand factor (vWf) concentrates may have certain advantages over treatment with nonheated products, if these preparations are efficacious in these disorders. We found that a commercially available factor VIII/vWf concentrate, Haemate P, contained the high-molecular-weight multimers of vWf and had a ratio of ristocetin cofactor (RCof) to vWf antigen (vWf:Ag) close to unity. In addition, its capacity to directly induce aggregation of platelet-type vWD platelets in vitro was similar to that for cryoprecipitate. When infused into a patient with platelet-type vWD, Haemate P shortened the prolonged bleeding time and caused spontaneous platelet aggregation in vitro with a mild diminution of platelet count. These results indicate that some of the heat-treated factor VIII/vWf concentrates may provide a safer, yet still effective, treatment for platelet-type vWD.