Coagulation factor levels were measured as previously described [11 (link)] and pooled mouse plasma was used to generate standard curves. Global coagulability of the plasma was determined by measuring the prothrombin time (PT) and activated partial thromboplastin time (aPTT) on the STart 4 analyzer (Diagnostica Stago, Leiden, The Netherlands) using the STA Neoplastine Plus (Diagnostica Stago) and the TriniCLOT Automated APTT reagent (TCoag, Ireland), respectively.
The in vivo clearance rates of human coagulation factors VII, VIII and IX were analyzed with home-made ELISAs specific for human proteins which did not cross-react with mouse plasma proteins. Standard curves were generated by adding Cofact or Aafact to pooled mouse plasma (final concentration 20%) to calculate human antigen levels, and the level measured directly after injection (1 minute) was set as a reference (100%).