Blood coagulation factors V and VIII are homologous proteins that have the domain organization A1-A2-B-A3-C1-C2. Upon thrombin activation, the B-domains of both molecules are released. Previous studies on factor VIII showed that the B-domain was not required for thrombin cleavage or activity. In contrast, deletion of the factor V B-domain (residues 709 to 1545) yielded a molecule with sevenfold...

1THE PARTIAL THROMBOPLASTIN TIME test was originally developed by Langdell et al. (1) as a method of following the therapy of hemophulic patients. These investigators found this test to be extremely sensitive to changes in Factor VIII brought about by whole blood or plasma transfusions. Extensive studies of the partial thromboplastin time test (PTT) by Rodman et il. (2) have shown that this tes...

von Willebrand factor (vWF) is a multimeric adhesive glycoprotein with one factor VIII binding site/subunit. Prior reports suggest that posttranslational modifications of vWF, including formation of N-terminal intersubunit disulfide bonds and subsequent cleavage of the propeptide, influence availability and/or affinity of factor VIII binding sites. We found that deletion of the vWF propeptide p...

Thrombocytopenic serum is a simple reagent derived from platelet-poor plasma. The high levels of factor V and ;zero' levels of factor VIII in this reagent make it a reliable alternative to haemophilia A plasma in the qualitative and quantitative assessment of factor VIII in the thromboplastin generation test.

Normal human plasma contains a complex of two proteins that are important in hemostasis and coagulation. The factor VIII procoagulant protein (antihemophilic factor) and the factor VIll-related protein (von Willebrand factor) are under separate genetic control, have distinct biochemical and immunologic properties, and have unique and essential T HE IMPORTANCE of factor VIII in hemostasis and bl...