Preparation of a human factor VII deficient plasma

Monoclonal antibodies to human factor VII: production of immunodepleted plasma for VII:C assays

A high affinity monoclonal antibody to factor VII (RFF-VII/1), coupled to sepharose, was used to immunodeplete factor VII from normal plasma. The plasma could be used as a substrate in a one stage coagulation assay and performed as well as, or better than, commercially available factor VII deficient plasma or plasma from congenitally deficient factor VII patients. Plasma from normal donors (n = 20), patients with liver disease (n = 20), and patients receiving warfarin (n = 20), or congenitally factor VII deficient patients (n = 7) was assayed for VII:C concentration in a one stage coagulation assay. The concentration of VII:C detected with the immunodepleted plasma substrate was comparable in all cases with that seen with a commercially available substrate (r = 0.95).

Application of factor VII-Sepharose affinity chromatography in the purification of human tissue factor apoprotein

Coagulation factor VII covalently coupled to Sepharose proved to be an effective binding ligand for human tissue factor apoprotein, the specific cofactor of factor VII for the activation of factor X and IX. This interaction is completely calcium-dependent and the calcium ions cannot be replaced by magnesium or barium ions. The binding of the apoprotein to immobilized factor VII seems to be independent of the presence of phospholipid. When factor VII-Sepharose column chromatography is combined with a mild extraction procedure, tissue factor apoprotein could be purified approximately 40,000-fold from an acetone powder of human brain. SDS-PAA gel electrophoresis revealed that with this simple purification scheme human tissue factor apoprotein can be purified to apparent homogeneity and that the apoprotein migrates at a molecular weight of 47,000. The isolated human protein is heterogeneously glycosylated; the two different forms of the apoprotein function as cofactor of factor VII in the activation of both factor X and factor IX.

Studies on immunological assay of vitamin K dependent factors. I. Measurement of factor VII antigen by radioimmunoassay

A radioimmunoassay (RIA) for factor VII was developed using 125I-factor VII, anti-factor VII rabbit serum and anti-rabbit IgG goat serum. The lower limit of sensitivity in normal reference plasma was 3 X 10(-3) units/ml. Although the level of factor VII antigen (VII:Ag) in normal plasma samples (n = 20) 0.944 +/- 0.176 units/ml, correlated with that of factor VII coagulant activity (r = 0.89), VII:Ag level in paired normal sera showed a higher value (1.469 +/- 0.376 units/ml). The level of antigen according to RIA of factor VIIa activated by factor Xa increased 2.5-fold compared with that of unactivated factor VII. It is suggested that the polyclonal anti-factor VII produced in a rabbit had higher affinity for factor VIIa than for factor VII. In two out of seven patients with congenital factor VII deficiency, VII:Ag was detectable (0.04, 0.31 units/ml, respectively) whereas VII:C was less than 0.01 units/ml. In 12 warfarin-treated individuals, VII:C showed a lower level (0.121 +/- 0.063 units/ml) that that of VII:Ag (0.518 +/- 0.186 units/ml). During 4 weeks observation after stopping warfarin, VII:C and VII:Ag reached normal levels in 1 week. However, VII:C did not reach equivalence with VII:Ag until 4 weeks had elapsed.

Hereditary blood coagulation factor-VII deficiency in the beagle: immunological characterisation of the defect

In the plasma of beagles known to be homozygotes for hereditary blood coagulation factor-VII deficiency, antibody neutralization assays indicate only slightly greater quantities of factor-VII related antigen than are detected by conventional assays of procoagulant activity. Plasma of one dog was depleted of factor-VII procoagulant activity by exposure to an immobilized antibody; the low level of activity originally present was then verified by titration with normal plasma. The plasma defect results from an incomplete deletion of synthesis.

Protein C, an anticoagulant protein, is increased in healthy volunteers and surgical patients after treatment with stanozolol

On both oral and intramuscular administration, the anabolic steroid stanozolol was found to increase protein C antigen concentrations in circulating blood. In fourteen healthy young volunteers (who received stanozolol orally, dose 10 mg/day) the average increase was 1.5-1.6 times the normal concentrations after 3-6 weeks' treatment and was accompanied by more moderate increases in the other vitamin K-dependent factors II, IX and X to 1.4, 1.4 and 1.2 times their normal concentration respectively. However, there was no change in factor VII. In sixteen elderly surgical patients, intramuscular injection (50 mg) one day prior to surgery induced a moderate increase within 24 hours (to 1.11 times the pretreatment concentration) and seven days after operation (to 1.19 times), and reduced the postoperative fall in protein C. Stanozolol administration seems to be a promising pharmacological method for increasing anticoagulant protein C levels in congenital and acquired deficiencies.

Congenital protein C deficiency and venous thromboembolism. A study of three Dutch families

Protein C is the zymogen of a vitamin K-dependent serine protease involved in blood coagulation. In the absence of protein C the inactivation of activated factors V and VIIIC is impaired, and the fibrinolytic capacity of the circulating blood is reduced. These conditions promote excessive fibrin formation and thus constitute a risk factor for thrombosis. Using an immunologic assay for protein C, we identified 18 patients (11 male and 7 female) in three unrelated Dutch families as fulfilling the criteria for an isolated protein C deficiency. In 12 patients who were not receiving oral anticoagulant treatment the mean protein C antigen concentration was 0.48 +/- 0.09 U per milliliter (+/- S.D.), and in 6 patients who were receiving adjusted doses of oral anticoagulants and had stable anticoagulation, the mean value was 0.17 +/- 0.05 U per milliliter. (The value in healthy subjects is 0.98 +/- 0.19 U per milliliter.) Fourteen of the 18 patients had a history of venous thromboembolism, with superficial thrombophlebitis as the hallmark of this condition (in 13 patients). These data are consistent with an autosomal dominant trait with variable expressivity.

Coagulation factors in the human fetus of about 20 weeks of gestational age

In plasma samples of 11 fetuses of about 20 weeks of gestational age the following coagulation factors have been determined (mean values found are given in parentheses): fibrinogen (0.30 U/ml), prothrombin (+/-0.17 U/ml), factor V (0.28 U/ml), factor VII (0.21 U/ml), factor VIII coagulant activity (factor VIII:C) (0.12 U/ml), factor VIII-related antigen (factor VIIIR:Ag) (1.04 U/ml), coagulant factor VIII-related antigen (factor VII:CAg) (0.19 U/ml), factor IX coagulant activity (0.05 U/ml), factor IX antigen (less than or equal to 0.03 U/ml), factor X (0,19 U/ml) and antithrombin III (AT-III) (0.23 U/ml). Our data support the evidence that prenatal diagnosis of haemophilia A is at present possible; less optimism is warranted where haemophilia B is concerned. the number of samples is sufficient to establish normal values for the age group. Means of quality control of the sample-which is often difficult to obtain-are disscussed.

Pathways in the activation of human coagulation factor X

Purified human Factor X (apparent mol.wt. 72000), which consists of two polypeptide chains (mol.wt. 55000 and 19000), was activated by both Russell's-viper venom and the purified physiological activators (Factor VII/tissue factor and Factor IXa/Factor VIII). They all convert Factor X to catalytically active Factor Xa (mol.wt. 54000) by cleaving the heavy chain at a site on the N-terminal region. In the presence of Ca2+ and phospholipid, the Factor Xa formed catalyses (a) the cleavage of a small peptide (mol.wt. 4000) from the C-terminal region of the heavy chain of Factor Xa, resulting in a second active form (mol.wt. 50000), and (b) the cleavage of a peptide containing the active-site serine residue (mol.wt. 13000) from the C-terminal region of the heavy chain of Factor X, resulting in an inactivatable component (mol.wt. 59000). A nomenclature for the various products is proposed.