Antibody-dependent dissociation of fVIII from vWF. Plasma-derived fVIII (0.5 U/mL) complexed to vWF (15:1 vWF to fVIII wt/wt ratio) was incubated for 60 minutes at 37°C in the presence of 5 μg/mL normal donor's polyclonal IgG (Nl IgG), of 0.5 μg/mL BO2C11 hu-MoAb (BO2C11), of 5 μg/mL patient BO's polyclonal IgG (BO IgG), or of buffer (-). The proportion of fVIII that remained bound to vWF was evaluated by capture of the fVIII-vWF complexes on a microtitration plate coated with the anti-vWF MoAb4H1D7. fVIII was then detected by the addition of the HRP-labeled anti-A2 MoAbF15B12. Control experiments showed that BO2C11 and BO's polyclonal IgG did not inhibit MoAbF15B12 binding to fVIII. The amounts of bound fVIII were calculated by comparison with a calibration curve established with known levels of insolubilised fVIII (see the Materials and Methods).