Binding of plasma fVIII to vWf.

Sepharose beads coated with anti-vWf moab75H4B12 were incubated with 10-fold diluted plasma. The beads were centrifuged, and fVIII present in supernatants was measured in a chromogenic assay. Control experiments were carried out with uncoated Sepharose beads. Results are expressed as the percentage of fVIII bound to vWf (Bound fVIII(%) = [fVIII in the supernatant of control Sepharose − fVIII in the supernatant of anti-VWF Sepharose] × 100/fVIII in the supernatant of control Sepharose). (A) Normal donor plasma fVIII; (B) plasma of patients with mild/moderate hemophilia A with mutations in the fVIII A1 or A2 domain; (C) plasma of a patient with mild/moderate hemophilia A with mutation in the fVIII A3 domain; (D) plasmas with fVIII mutations in the C1 domain. Each value represents the mean of at least 2 experiments and SDs are as indicated. Values of vWf-bound fVIII significantly lower than that of normal fVIII are indicated: *P < .025; **P < .01.