Recombinant factor VIII and factor IX concentrates, human-plasma-derived albumin, and samples from previously untreated patients with hemophilia were examined for the presence of TT virus (TTV) by using polymerase chain reaction testing. Blood samples from the patients were obtained prospectively before and every 3 to 6 months after therapy was begun. TTV was detected in 23.5% of the recombinan...

A localized and regulated cascade of proteolytic events is a prerequisite for normal haemostasis. The activation of factor X by activated factor IX (factor IXa) in the presence of activated factor VIII (factor VIIIa) is essential for the formation of a fibrin clot at sites of vascular injury. We observed sustained activation of factor X on the surface of vascular endothelial cells, whereas, in ...

Factor VIII C-domains are believed to have specific functions in cofactor activity and in interactions with von Willebrand factor. We have previously shown that factor VIII is co-targeted with von Willebrand factor to the Weibel-Palade bodies in blood outgrowth endothelial cells, even when factor VIII carries mutations in the light chain that are associated with defective von Willebrand factor ...

Coagulation factor VIII (FVIII) is a cofactor in the intrinsic pathway of blood coagulation for which deficiency results in the bleeding disorder hemophilia A. FVIII contains a domain structure of A1-A2-B-A3-C1-C2 of which the B domain is dispensable for procoagulant activity in vitro. In this report, we compare the properties of B-domain-deleted FVIII (residues 760 through 1639, designated LA-...

Plasmin not only functions as a key enzyme in the fibrinolytic system but also directly inactivates factor VIII and other clotting factors such as factor V. However, the mechanisms of plasmin-catalyzed factor VIII inactivation are poorly understood. In this study, levels of factor VIII activity increased approximately 2-fold within 3 min in the presence of plasmin, and subsequently decreased to...

The complement protein C4b-binding protein plays an important role in the regulation of the protein C anticoagulant pathway. C4b-binding protein can bind to protein S, thereby inhibiting the cofactor activity of protein S for activated protein C. In this report, we describe a new role for C4b-binding protein in coagulation. We observed inhibition of the intrinsic factor X activating reaction by...