The Defect in Hemophilic and von Willebrand's Disease Plasmas Studied by a Recombination Technique

Factor VIII in preparations from normal plasma is a large glycoprotein of greater than 2 million molecular weight which elutes in the exclusion volume of 4% agarose gels at an ionic strength of 0.15. Recent studies have demonstrated that the factor VIII in canine and bovine plasma is a macromolecular complex composed of a large inert carrier protein and a noncovalently bound small fragment which contains the procoagulant active site. This complex is dissociable in 0.25 M CaCl₂, and conditions for its recombination have been reported. The present study reports the dissociation characteristics of normal human factor VIII preparations in 0.25 M CaCl₂ and the ability to achieve quantitative recombination of the dissociated fragments of normal human and bovine factor VIII after the removal of Ca²⁺. The recombination technique was used to characterize further the defect in hemophilia and von Willebrand's disease. Void volume preparations from human hemophilia A^-, canine hemophilia A, and human von Willebrand's plasma, with no factor VIII procoagulant activity, were mixed with the small active fragment prepared from the normal plasma of their respective species. Chromatography of the three mixtures in agarose gel showed that the fractions from the human hemophilic plasmas contained a molecule that bound the small active normal fragment, but neither the fractions from canine hemophilia A plasmas nor the fractions from the human von Willebrand's plasmas demonstrated evidence of such material. These data suggest that there is present in human hemophilia A plasma a normal functional carrier molecule which is absent or nonfunctional in the plasma of hemophilic dogs and humans with von Willebrand's disease.

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