Immunoradiometric assay of factor VIII related antigen, with observations in 32 patients with von Willebrand's disease

Anti-idiotypic suppression of autoantibodies to factor VIII (antihaemophilic factor) by high-dose intravenous gammaglobulin

In two patients with high-titre autoantibodies to antihaemophilic factor (VIIIc), treatment with high-dose intravenous immunoglobulin (IVIg) resulted in rapid and prolonged, although not total, suppression of antibody. IVIg also inhibited anti-VIIIc activity in patients' plasma in vitro; IVIg and F(ab')2 fragments from IVIg inhibited anti-VIIIc activity of the IgG fraction and of the Fab'2 fragments of the IgG fraction from patients' plasma, indicating that the in-vivo effect of IVIg was due to the presence in the therapeutic immunoglobulins of anti-idiotypic antibodies against idiotypes expressed by anti-VIIIc autoantibodies. In contrast, IVIg had little or no effect on antibody titre in two haemophilic patients with anti-VIIIc alloantibodies. These observations suggest that IVIg contains anti-idiotypes against autoantibodies and may be effective in the treatment of some autoimmune diseases through idiotypic/anti-idiotypic interactions.

Isolation of a storage and secretory organelle containing Von Willebrand protein from cultured human endothelial cells

Von Willebrand protein was synthesized and secreted by human endothelial cells in culture. Ca2+ ionophore A23187 and phorbol myristate acetate stimulated the release of Von Willebrand protein from the cultured cells. Stimulated release was accompanied by the disappearance of rod-like structures from the cultured endothelial cells immunostained for Von Willebrand protein, suggesting the existence of a storage organelle for Von Willebrand protein in these cells (Loesberg, C., Gonsalves, M.D., Zandbergen, J., Willems, C., Van Aken, W.G., Stel, H.V., Van Mourik, J.A. and De Groot, P.G. (1983) Biochim. Biophys. Acta 763, 160-168). Cultured human endothelial cells were fractionated on a density gradient of colloidal silica. Von Willebrand protein was found in two organelle populations: a buoyant one sedimenting with a variety of cell organelle marker enzymes, including those of the Golgi apparatus, mitochondria, lysosomes, peroxisomes, endoplasmic reticulum and plasma membrane fragments (peak density of this fraction: 1.08 g X ml-1), and a dense one with a peak density of 1.12 g X ml-1. The dense organelles containing Von Willebrand protein were apparently free of other organelles. Stimulating Von Willebrand protein release with phorbol myristate acetate or Ca2+ ionophore A23187 resulted in a decrease or even complete disappearance of Von Willebrand protein from the high-density organelle fraction, implying a role of this organelle in the stimulus-induced release of Von Willebrand protein. The Von Willebrand protein content of the buoyant fraction was lowered to some extent or did not change upon incubation of the cells with ionophore A23187 and phorbol myristate acetate. Restoration of Von Willebrand protein content of the dense organelle fraction after stimulation occurred within 2 days; this was accompanied by recurrence of immunostaining of rod-shaped structures in cells and an increase in cellular Von Willebrand protein. The excretion of restored Von Willebrand protein could be stimulated again.

The interaction between factor VIII clotting antigen and phospholipids in genetic variants of hemophilia and von Willebrand's disease

The interaction of factor VIII with phospholipids was investigated in 11 patients with mild and moderate hemophilia A, 7 patients with von Willebrand's disease and in 10 healthy people as controls. The addition of phospholipid vesicles containing phosphatidylserine and phosphatidylethanolamine to normal plasma and that of patients with von Willebrand's disease resulted in the loss of almost two thirds of the factor VIII clotting antigen (VIII:CAg) measurable by IRMA. Defective interaction of phospholipids with VIII:CAg was noted in some genetic variants of mild and moderate hemophilia A. Thus four of the five families tested showed decreased binding of VIII:CAg to phospholipids. One of the families tested belonged to a genetic variant with much more VIII:CAg than VIII:C, and it was in members of this family that the binding capacity was most reduced. The most probable explanations for the defective interaction with phospholipids is that molecular defects of VIII:CAg result in either decreased binding to phospholipids or might lead to a stronger binding between VIII:CAg and the von Willebrand factor (VIIIR:Ag) in the factor VIII complex and thereby preventing the normal separation of the complex.

Atherosclerosis and von Willebrand factor. I. Prevalence of severe von Willebrand's disease in western Europe and Israel

The prevalence of von Willebrand's disease (VWD) in Western European countries and Israel was assessed. Possible patients were identified initially by questionnaire and those with plasma levels of von Willebrand factor antigen ( WFAg ; factor VIII related antigen) less than 1 u/dl (less than 1%) were confirmed by immunoradiometric assay performed at four reference centres. The prevalences of severe VWD in Scandinavian countries were similar to each other and about 10 times greater than those in other Western European countries. The prevalence in Israel was intermediate. The Registry will form the basis for future non- invasive epidemiological studies of atherosclerosis in these individuals.

Measurement of factor VIIIRAg-1. A method for use in the Hyland laser nephelometer

Factor VIIIRAg was measured by laser nephelometry using a new diluent containing a citrate-carbonate buffer, pluronic polyol P94 and triton X100. No pre-treatment of the samples was required, the incubation time was 0.5 to 1.5 hours depending on the antiserum used, and the tests could be read during the following 4 hours (plasma) or 1.5 hours (intermediate purity F VIII). The CV for the assay was less than 10% for plasma or dilutions of plasma in which the minimum detectable amount of factor VIIIRAg was about 0.04 u/ml. A significant correlation was obtained between the nephelometric method and the Laurell rocket method using plasma, but agreement between the methods when therapeutic products were assayed was poor.

The effect of lipoproteins on the synthesis of prostacyclin, von Willebrand factor and apolipoproteins A-I and A-II in cultured human endothelial cells

Primary cultures of confluent human endothelial cells (ECM) were grown in media containing the major lipoproteins (LP) and lipoprotein deficient serum (LDS). The release of 6-keto-PGF1 alpha, von Willebrand factor (VIII RAg) and apolipoproteins (apo) A-I and A-II were investigated by radioimmunoassay. The cell-associated VIII RAg, apo A-I and apo A-II were also confirmed by fluorescein antibodies, and the synthesis of the apolipoproteins was examined by incorporation of [3H]leucine. Apo A-I and apo A-II were located and synthesized in ECM, yet only apo A-I was released into the medium. Very low density (VLDL) and low density lipoproteins (LDL) in concentrations of 50-600 micrograms/ml stimulated release of apo A-I. Stimulation of ECM for 5 min with thrombin (T) or arachidonic acid (A) did not induce apo A-I release. VIII RAg was always released into the media from ECM. The release was not affected by the lipoproteins. VIII RAg was also localized on the cell surface (VIII RAgC) and approximately 80% was released by trypsin. LDL stimulated the occurrence of factor VIII RAg on the cell surface. 6-Keto PGF1 alpha was always released into the medium and the production was stimulated by T and AA. The main lipoproteins (50-600 micrograms/ml) and apo A-I and A-II did not affect the release of 6-keto-PGF1 alpha. This study shows that endothelial cells synthesize and release proteins important for thrombogenesis and atherosclerosis. The release of apolipoproteins A-I was stimulated by VLDL and LDL, and the concentration of cell-related factor VIII RAg was stimulated by LDL.

Platelet aggregation induced by 1-desamino-8-D-arginine vasopressin (DDAVP) in Type IIB von Willebrand's disease

Type IIB von Willebrand's disease is a distinct form of this disorder, in which there are abnormal factor VIII/von Willebrand factor multimers in plasma (but normal multimers in platelets) and heightened interaction between the von Willebrand factor and platelets in the presence of ristocetin. We have found that infusion of desmopressin acetate (1-desamino-8-D-arginine vasopressin [DDAVP]), an agent used in the treatment of von Willebrand's disease, causes platelet aggregation and thrombocytopenia in patients with Type IIB disease. In vitro, platelets in normal plasma and those obtained from patients with Type IIB disease before DDAVP infusion aggregated upon the addition of platelet-poor plasma from Type IIB patients treated with DDAVP. Platelet aggregation was associated with adsorption of multimers of factor VIII/von Willebrand factor onto the platelets and was inhibited by EDTA. We conclude that in Type IIB von Willebrand's disease, DDAVP releases an abnormal factor with platelet-aggregating properties. DDAVP should not be used to treat patients with Type IIB disease, since the presence of platelet aggregates in the circulation may be harmful.

A cellulose sandwich fluoroimmunoassay for Factor VIII-related antigen

We describe a cellulose sandwich fluoroimmunoassay for Factor VIII-related antigen (FVIIIR:Ag). Plasma is incubated with cellulose-antibody for 2 hours, fluorescent-labelled antiserum is added and the samples are allowed to react for an additional 2 hours. The fluorescence associated with the cellulose-antibody is measured after the tubes have been centrifuged, and the deposit washed and then digested with sodium hydroxide. Ninety-seven samples are assayed and the results are compared with radioimmunoassay (correlation coefficient 0.960) or electroimmunoassay (correlation coefficient 0.882). Between-run coefficients of variation are 8.0% to 9.9%. The cellulose-antibody reagent and the fluorescent-labelled antiserum were both stable over a period of 1 year, demonstrating a major advantage of fluoroimmunoassay over radioimmunoassay.

Deamino-8-D-arginine vasopressin shortens the bleeding time in uremia

In a randomized double-blind cross-over trial we gave either 1-deamino-8-D-arginine vasopressin or placebo to 12 patients with uremia, hemorrhagic tendencies, and prolonged bleeding times. After vasopressin infusion, all patients had shortened bleeding times, with the effect lasting for at least four hours in most cases. Platelet count, platelet cyclic AMP levels, platelet retention on glass beads, plasma fibronectin, serum thromboxane B2 and residual prothrombin, hematocrit, and plasma osmolarity were unchanged after vasopressin. A consistent post-infusion increase in factor VIII coagulant activity and, to a lesser extent, in factor VIII-related antigen and ristocetin cofactor accompanied the shortening of bleeding time. In addition, vasopressin induced the appearance in plasma of larger von Willebrand-factor multimers than those present in the resting state. The compound was given to nine additional patients with acute or chronic renal failure and prolonged bleeding times, before major surgery or renal biopsy. In these patients, shortening of the bleeding time was associated with normal hemostasis. Our findings indicate that 1-deamino-8-D-arginine vasopressin can be used for temporary correction of bleeding time and may prevent surgical bleeding in patients with uremia.

The effect of storage of whole blood on the association of factor VIII-related antigen and factor VIII-coagulant antigen

To evaluate the extent of denaturation of factor VIII-coagulant activity (VIII: C) during production of factor VIII concentrates, the factor VIII-coagulant antigen (VIII: CAg)/VIII: C ratio was measured in plasma, cryoprecipitate and cryosupernatant from fresh and stored blood. This ratio was close to unity for both cryoprecipitate and other concentrates, suggesting that VIII: CAg is lost concurrently with VIII: C during cryoprecipitation and further fractionation. Storage of blood (18 h, 22 degrees C) before processing resulted in a 30% loss of VIII: C from the separated plasma; however, VIII: CAg was not affected. In cryoprecipitate prepared from this plasma, VIII: C and VIII: CAg both were 30% lower than when prepared from fresh plasma. In the corresponding cryosupernatant, however, more VIII: CAg but less VIII: C was present compared with fresh material. Gel chromatography revealed that the rise of VIII: CAg in cryosupernatant prepared from stored blood, was due to an increased amount of VIII: CAg of low molecular weight, not being associated with factor VIII-related antigen. Such an increase in dissociated VIII: CAg was not detected in the plasma prior to cryoprecipitation. It is concluded that during storage of blood, molecular changes are induced in the factor VIII-VWF complex, possibly by limited proteolysis, which make the complex more liable to dissociation during subsequent cryoprecipitation.

Simplified immunoradiometric assay for factor VIII coagulant antigen

A simplified, non-competitive, solid phase immunoradiometric assay has been developed for the quantitation of factor VIII coagulant antigen (VIII:CAg)--the antigenic counterpart of FVIII coagulant activity (VIII:C). Both homologous and heterologous antibodies to human factor VIII (FVIII) were used in this assay. Initially, FVIII in a test sample was attached to immobilized, human IgG obtained from a polytransfused haemophilia A patient with a high titre antibody to VIII:C. The bound FVIII was then detected using rabbit 125I-IgG specific for human FVIII. The concentration of VIII:CAg correlated well with VIII:C levels in the plasma from normal donors (r = 0.84, n - 15). Homozygote von Willebrand's disease patients had undetectable levels of VIII:CAg in their plasma. Patients with severe haemophilia A (VIII:C less than 0.01 u/ml) could be divided into groups on the basis of the VIII:CAg levels, i.e. those having undetectable VIII:CAg and other with measurable VIII:CAg. VIII:CAg detected in normal serum was less than 0.002 u/ml. In this assay the use of human antibody to FVIII is considerably decreased compared to other methods for VIII:CAg, and the time-consuming steps to immunopurify human anti-FVIII antibody are eliminated.

Alterations of factor VIII von Willebrand factor in clinical conditions associated with an increase in its plasma concentration

Factor VIII-related antigen (VIIIR:Ag) was consistently higher than factor-VIII procoagulant activity (VIII:C) in 57 patients with clinical conditions characterized by acute-phase reactions. Two different methods for measuring VIII:C (one- and two-stage assays) and VIIIR:Ag (electroimmunodiffusion and immunoradiometric assay) gave concordant results in the majority of cases. In 43% of plasma samples, crossed immunoelectrophoresis in agarose gel was characterized by the appearance of an additional, fast-moving precipitin peak which was immunologically identical with the major, slower-moving VIIIR:Ag peak. The fast-moving peak was detected in all the patients with clinical conditions typically associated with increased plasma proteolysis (DIC, acute pancreatitis, during thrombolytic therapy). It was present in a smaller proportion of cases with liver and renal failure and malignancies and in the post-operative period. The additional VIIIR:Ag peak is thought to be the result of in vivo factor VIII/von Willebrand factor fragmentation by proteolytic enzymes.

Partial purification of biologically active, low molecular weight, human antihemophilic factor free of Von Willebrand factor. I. Partial characterization and evidence for disulfide bond(s) susceptible to limited reduction

Partially purified (approx. 5000-fold), low molecular weight human antihemophilic factor, free of detectable Von Willebrand factor (ristocetin cofactor activity or Von Willebrand antigen), was prepared from fresh citrated plasma by limited reduction with 1 mM dithiothreitol and chromatography on Sepharose CL-4B, Sephadex G-100, and polyelectrolyte E-5. The ratio of antihemophilic factor activity to Von Willebrand factor activity or antigen was greater than 27 000 : 1. The antihemophilic factor activity could be neutralized with homologous antibody and could be further increased with thrombin. The Mr (approx. 116 000) was determined by calibrated gel permeation chromatography, electrophoresis in 5% polyacrylamide gels with sodium dodecyl sulfate and by electrophoresis in large-pore acrylamide gels without it. Since the low Mr antihemophilic factor could be prepared by treating fresh rather than fresh-frozen plasma with dithiothreitol, it was concluded that partial reduction of the antihemophilic factor with this reagent helped to maintain the antihemophilic factor in a low Mr form. When iodo[l-14C]acetamide was used to alkylate the reduced plasma proteins prior to purification, the molecular weight of the purified antihemophilic factor remained low despite numerous purification steps. By this means, one of four radioactive proteins (Mr 116 000) in the final preparation was bound specifically to homologous antihemophilic factor antibody and attributed to 14C-labeled antihemophilic factor. While the data suggest that antihemophilic factor in fresh plasma contains one or more dithiothreitol-sensitive intramolecular disulfide bonds, the possibility of disulfide linkages with other proteins(s) cannot be excluded.

Synthesis and release of factor VIII by cultured human endothelial cells

Endothelial cells (ECs) derived from human umbilical veins were cultured in order to study the physiological control of factor VIII synthesis and release. The culture media were studied from multiple replicate cultures at confluence. Factor VIII related antigen (VIIIR:Ag) and factor VIII coagulant antigen (VIII:CAg) were measured by sensitive immunoradiometric assays. De novo synthesis of factor VIII related protein (VIII:R) was quantitated by incorporation of labelled amino acids into specific protein subunits. The following agents were added to the culture medium in a range of concentrations from physiological to pharmacological: adrenaline, 5 hydroxytryptamine, 2,3-DPG, cyclic AMP, thyroxine, hydrocortisone, and human growth hormone. None of them had any effect at any concentration on the rate of accumulation of VIIIR:Ag in the culture medium. Addition of exogenous factor VIII had no effect on do novo synthesis of VIII:R. VIII:CAg was found to be stable under the conditions of culture but none was released from the ECs. Long-term monocyte cultures also failed to release VIII:CAg. It appears that VIII:R is a constitutive gene product of umbilical vein endothelial cells and that VIII:CAg is not made by these cells.

Factor VIII:C and VIII:CAg response in patients with haemophilia A and von Willebrand's disease after administration of different factor VIII concentrates or plasma

Factor VIII procoagulant activity (VIII:C) and factor VIII procoagulant antigen (VIII:CAg) were studied in seven patients with haemophilia A after administration of three different factor VIII concentrates or plasma. The in vivo recovery of VIII:CAg was less than that of VIII:C and the disappearance rate of VIII:CAg was much higher either when concentrates or plasma were given. The half-life of VIII:C was thus about 12 h but of VIII:CAg only about 3 h or less. Six patients with von Willebrand's disease were studied after administration of AHF-Kabi. In contrast to haemophilia A the discrepancy between VIII:C and VIII:CAg disappearance rates was not present in von Willebrand's disease, since both VIII:C and VIII:CAg showed a typical progressive increase. We conclude that factor VIII:C given to haemophilia patients does not behave like native VIII:C, not even when fresh plasma is used. Patients with von Willebrand's disease are capable of forming a normal VIII:C when appropriately stimulated.

New methods in coagulation

Recent advances in the elucidation of the molecular biochemistry of the coagulation proteins have provided the foundation for the development of synthetic substrates. These substrates are oligopeptide with either a chromophore or fluorophore group attached to the C-terminal end. They may be used in the laboratory to assay for a number of the serine proteases involved in either coagulation or fibrinolysis. Also, by suitably modifying the assay system, the various inhibitors can be quantitated. These substrates promise to revolutionize the coagulation laboratory allowing for more precise quantitation of trace enzymes and also improved standardization and precision of coagulation assays. In addition to these substrates, the introduction of a number of immunologic procedures into the diagnostic laboratory have been of major importance in elucidating the heterogeneity of hereditary coagulation defects. By correlating the immunologic assays, coagulation assays and clinical picture, a number of subgroups of hereditary deficiencies have been identified. Also, the immunologic assays have provided a means for identifying the carrier state of hemophilia A and have significantly contributed to the improved diagnosis of von Willebrand's disease. The use of ristocetin cofactor assays, when used in conjunction with the Factor VIII antigens, have enable the laboratory to more accurately diagnose the majority of patients with von Willebrand's disease. Ristocetin cofactor may be assayed utilizing either formalin fixed or washed platelets and recently a snake venom has been introduced to assay for this particular aspect of the Factor VIII complex. Platelet specific proteins (i.e., platelet factor 4 and beta-thromboglobulin) may be assayed utilizing either radioimmunoassays or in the case of platelet factor 4 modified coagulation assays. These proteins provide evidence of in vivo platelet activation and hopefully may, in the future, be correlated with platelet kinetics.

Heightened interaction between platelets and factor VIII/von Willebrand factor in a new subtype of von Willebrand's disease

The form of von Willebrand's disease characterized by a qualitative abnormality of Factor VIII/von Willebrand factor (FVIII/vWF) in plasma has been designated as Type II. We have now identified 20 persons from five families whose qualitatively abnormal FVIII/vWF shows heightened responsiveness to ristocetin. We have classified this form of the disease as Type IIB and reclassified as Type IIA the form previously described as Type II, in which the interaction of the abnormal FVIII/vWF with platelets is decreased or absent in the presence of ristocetin. The enhanced reactivity of FVIII/vWF in Type IIB was evident in studies of ristocetin-induced platelet agglutination and of binding of FVIII/vWF to platelets in the presence of ristocetin. In both Type IIA and IIB, crossed immunoelectrophoresis of plasma FVIII/vWF demonstrated similar absence of the larger, less anodic forms. These findings suggest that ristocetin-mediated interactions between platelets and FVIII/vWF do not accurately reflect the "bleeding-time" (von Willebrand factor) defect in this newly described subtype of von Willebrand's disease.

Characteristics of the factor VIII protein and Factor XIII in various factor VIII concentrates

The in vitro properties of 5 factor VIII preparations (AHF-Kabi, Hemofil Hyland, AHF-Profilate Abbott, Kryobulin Immuno and Factorate High Purity Armour) and an ordinary cryoprecipitate were studied with reference to factor VIII clotting activity (VIII:C), factor VIII clotting antigen (VIII:CAg), factor VIII related antigen (VIIIR:Ag) (EI, IRMA, CIE), ristocetin cofactor activity (VIIIR:RCF), fibrinogen and factor XIII. All the preparations with the exception of Factorate had higher levels of VIII:CAg than VIII:C indicating inactivation of the biological activity of VIII:C during the procedure. AHF-Kabi (fraction I-0) and the cryoprecipitate, the only preparations capable of normalising the defect in patients with von Willebrand's disease, showed the same level of VIIIR:Ag determined by EI and by IRMA, while all the other preparations (i.e. cryoprecipitates purified further in different ways) had considerably lower levels of VIIIR:Ag determined by IRMA than by EI. Based on these in vitro techniques it seems to be possible to predict which preparations can be used successfully in patients with von Willebrand's disease, while no such conclusions can be made from VIIIR:RCF determinations. EI yielded similar concentrations of factor XIII a subunit in all the preparations tested. 3 functional assays showed high factor XIII activities in AHF-Kabi but low or no activities in the others. Thus, considerable differences were found on the in vitro properties of the proteins in 5 factor VIII concentrates and a cryoprecipitate. The action of proteases and the techniques used in the purification procedure are probably of crucial importance for the properties of the various factors.

Fanconi's anaemia associated with haemophilia A

Fanconi's anaemia and haemophilia A are born inherited diseases creating haemostatic defects. The association of these two rare diseases in one patient is described. The patient's haemophilia was studied with a newly developed immunological technique determining the plasma antigen associated with Factor VIII activity, and was found to be a genetic variant of moderately severe haemophilia A. It was not possible to demonstrate a common bone marrow defect or a common immunological or genetical background of the two diseases. The double haemostatic defect created, i.e. Factor VIII deficiency and thrombocytopenia, resulted in only a slight increase in bleeding tendency. A favourable result was obtained with corticosteroid and androgenic treatment.

Measurement of antihaemophilic factor A antigen (VII:CAg) with a solid phase immunoradiometric method based on homologous non-haemophilic antibodies

Antihaemophilic-factor-A-antibodies, which had spontaneously arisen in 2 patients, were used to develop an immunoradiometric method for measurement of antihaemophilic factor A antigen (VIII:CAg). 13 patients with severe haemophilia A had VII:CAg below the limit of detection (0.01 U/ml). Patients with moderate and mild haemophilia A either had VII:CAg roughly equal to factor VIII clotting activity (VIII:C) or a not detectable VII:CAg, suggesting 2 different molecular mechanisms in moderate and mild haemophilia A. VIII:CAg could be detected in serum but in lower amounts than in plasma. In 2 patients with von Willebrand's disease VIII:CAg equalled VII:C. The post-transfusional retarded increase of VII:C in 1 patient with von Willebrand's disease was accompanied by a slight increase in VIII:CAg. Fetal plasma contained measurable amounts of VII:CAg.

The separation of Willebrand factor from factor VIII-related antigen

The three activities associated with factor VIII--coagulant (VIII:C), antigenic (VIIIR:Ag), and platelet agglutinating or Willebrand factor (VIIIR:WF)--have been separated by sequential antibody affinity chromatography, utilizing a rabbit antibody to factor VIII and a spontaneous human antibody to VIII:C. Normal plasma differentially lost its factor VIII-related antigen following passage over the rabbit antibody column. Subsequent passage of the VIIIR:Ag-depleted plasma over the human antibody column resulted in the loss of VIII:C activity, with retention of the Willebrand factor activity, antigen being partially recovered from the heterologous antibody column. These experiments demonstrate that it is possible to separate two of the factor VIII activities, VIIIR:Ag and VIIIR:WF, which are usually regarded as properties of a single molecule.

An immunoradiometric assay for procoagulant factor VIII antigen: results in haemophilia, von Willebrand's disease and fetal plasma and serum

An immunoradiometric assay (IRMA) has been developed based on the inhibitor which arose in a polytransfused severe haemophiliac. The two-site IRMA measures antigens closely associated with the procoagulant parts of the factor VIII complex, which are termed FVIIC antigens or FVIIICAG. FVIIICAG was present in normal plasma and also, at a slightly lower concentration, in normal serum. In 37 patients with haemophilia A, 36 had FVIIICAG levels of less than 10% of the normal plasma pool. In patients with von Willebrand's disease the levels of FVIIIC and FVIIICAG were in good agreement, both before and after treatment with cryoprecipitate or DDAVP. FVIIICAG was relatively stable in plasma at 37 degrees C and could also be detected in cord and fetal serum. The assay is of potential value for detecting reduced levels of factor VIII, for carrier detection and for the prenatal diagnosis of haemophilia.

Classification of von Willebrand's disease

The classification of von Willebrand's disease should be based primarily on the mode of inheritance: thus, the main division would between autosomal dominant and autosomal recessive types. Phenotypic subdivisions within these major types may then be possible. A subgroup of the dominant type seems to be well defined by increased electrophoretic mobility of the VIII-related antigen.

Use of a simple visual assay of Willebrand factor for diagnosis and carrier identification

A visual assay of factor VIII-related Willebrand factor (VIIIR:WF) is described which utilizes formaldehyde-fixed platelets, end points being read in microflocculation tiles. Four dilutions of a sample can be assessed simultaneously, and the correlation with aggregometric assays is high (r = 0.91). Measurement error is 8.0% for a single assay in triplicate and less than 5% if an assay is repeated three times. The method has been used for 2 years by the coagulation genetics group at Chapel Hill for diagnosing subjects with von Willebrand's disease and assigning genotypes to members of families transmitting this disorder. Its utility in classifying known carriers of haemophilia A has also been examined, both in conjunction with assays of VIII:C and in a three-way test with assays of VIII:C and VIIIR:Ag. As predicted by the Lyon hypothesis, the rate of false negative diagnosis was higher than false positive diagnosis, but the overall rate of misclassification on single plasma samples was 7/51 = 13.7%. The error rate was the same whether discrimination was based upon assays of VIII:C vs. VIIIR:Ag, VIII:C vs. VIIIR:WF, or VIII:C vs. VIIIR:Ag vs VIIIR:WF, the same individuals being misclassified by each method. The observed rate of misclassification was well within the rates reported by others and very similar to our previous experience. We have concluded that this method of assaying VIIIR:WF is highly useful for diagnosing vWd, detecting inhibitors to VIIIR:WF, and examining large numbers of column fractions. It is a useful supplement, although it cannot yet substitute for, assays of VIIIR:Ag in detecting carriers of haemophilia A.

Coexistence of haemophilia A and von Willebrand's disease in the same kindred

A clinical and laboratory investigation of a kindred in which haemophilia A and autosomal recessive von Willebrand's disease (VWD) were concomitantly present is described. 3 male patients were shown to be hemizygotes for moderate haemophilia A, one female appeared to be haemophilia A carrier and 3 males showed laboratory findings consistent with heterozygosity for autosomal recessive VWD. In one woman, the pedigree and laboratory findings suggest the possibility of double heterozygosity.

Factor IX antigen by radioimmunoassay. Abnormal factor IX protein in patients on warfarin therapy and with hemophilia B

Factor IX, isolated from normal human plasma, was homogenous by polyacrylamide gel electrophoresis in urea and sodium dodecyl sulfate. On the latter, it migrated as a single polypeptide chain with or without reducing agents and had an apparent mol wt of 62,000. After iodination by chloramine-T, a single peak of 125I was found on gels. Immunoelectrophoresis in agarose with rabbit antifactor IX sera gave a single arc against both isolated and partially purified factor IX preparations. The rabbit antibody was specific as it failed to inhibit the activities of prothrombin or factors VII or X in normal plasma. At an additional 20-fold dilution, factor IX activity was inhibited 50%. In a double-antibody radioimmunoassay, excess rabbit anti-human factor IX precipitated 90-95% of the 125I-human factor IX. Control without specific antibody gave 6-8%. Dilutions of a pool of normal human plasma paralleled dilutions of the isolated preparation and were used for the standard curve. Of 39 plasma samples from normal donors, the mean factor IX antigen level was 93% of that of a separate normal pool. The radioimmunoassay detected the abnormal factor IX produced in patients on warfarin therapy. After Al(OH)3 adsorption of warfarin treated patient's plasma, factor IX antigen, but not activity, was present in the supernate. Samples from 28 patients on warfarin gave a mean factor IX clotting activity of 27% with a mean antigen of 69%. The antigen level from the warfarin group was significantly lower than the antigen level of the normal group (P less than 0.001). The factor IX antigen level was then assessed in 36 patients from 29 pedigrees with hemophilia B. The median antigen level was 17% of normal. The distribution of the antigen level was wide with two patients around 100% of normal; only two had levels below the limits of resolution of the radioimmunoassay as currently performed (less than 2%). Within each of the five pedigrees in which more than one affected member was tested, activity and antigen levels were the same. The degree of neutralization of the antibody's inhibition of normal plasma by patient's plasma was highly correlated. Additional evidence for the detection of abnormal protein was provided by immunodiffusion of plasmas concentrated by lyophilization. Reactions of complete identity occurred between normal, a warfarin treated and a hemophilia B subject's plasmas.

1-Deamino-8-d-arginine vasopressin: a new pharmacological approach to the management of haemophilia and von Willebrands' diseases

1-Deamino-8-d-arginine vasopressin (D.D.A.V.P.) infusion causes a marked increase in factor-VIII (antihaemophilic-factor)-related properties in patients with moderate and mild haemophilia and von Willebrand's disease (vWd). The possibility was therefore evaluated that such an autologous factor-VII response might be haemostatically effective, allowing patients to undergo surgery without plasma concentrates. 0.3 microng/kg of D.D.A.V.P. given before dental surgery and repeated in the early postoperative period was followed by a two to three fold rise in factor-VIII coagulant activity (VII C.A.) in four patients with moderate and mild haemophilia. In two, there was no abnormal bleeding after dental extraction, whereas plasma concentrates were necessary to control oozing from the sockets in the remaining two patients. A higher D.D.A.V.P. dosage (0.4-0.5 microng/kg) in patients with higherstarting VII C.A. (9% or more) was followed by a more marked response (four to six fold). VII C.A. levels up to 100% of average normal were achieved and dental extraction and major surgery (such as cholecystectomy, thoracotomy, and two tonsillectomies) were carried out successfullly in six patients with mild haemophilis and in two with vWd. The mean half-life of autologous VII C.A. was 9.4 h (range 7.5-11.6). Plasma and urine osmolality showed no consistent variation after drug administration. Thus D.D.A.V.P. appears a promision pharmacological alternative to plasma concentrates in the management of some patients with haemophilis and vWd.

Spectrum of von Willebrand's Disease: a study of 100 cases. Italian Working Group

The clinical picture, family history and laboratory findings of 100 patients with von Willebrand's disease (VWD) have been studied in Italy in a multicentre survey from two rural areas with a known high incidence of the disease and from two large cities (Rome and Milan). Bleeding time, procoagulant factor-VIII (VIIIAHF) assay, platelet retention and PRP-ristocetin aggregation were measured in each centre, and plasma samples were frozen and subsequently assayed for factor VIII-related antigen (VIIIAGN) and ristocetin co-factor (VIIIVWF) in one laboratory (Milan). On the basis of the inheritance pattern, clinical severity of the disease and laboratory findings, patients with VWD were separated into two groups. In 17 patients the absence of a family history of bleeding, a high incidence of parental consanguinity and involvement of both sexes suggested an autosomal recessive mode of inheritance; the unusual severity of the disease with markedly abnormal results of all six laboratory measurements (and frequent reduced levels of VIIIAGN and VIIIVWF in the unaffected parents) were consistent with the homozygous state. In 83 patients, the disease was familial (being transmitted as an autosomal dominant trait) and of moderate clinical severity. In these, VIIIVWF was usually much lower than VIIIAHF and VIIIAGN. The findings suggest that although some patients may present with simultaneous abnormalities of all six studied laboratory measurements, the majority show a variation in the spectrum of the abnormal results, without any obvious simple pattern.