Inhibition of fVIII activity in the factor Xase assay by MoAb CLB CAg A and inhibitor MU. FVIII (2 nmol/L) was preincubated with increasing concentrations of inhibitor MU (•) or MoAb CLB-CAg A (○) IgG for 30 minutes at 37°C followed by determination of fVIII activity in the chromogenic factor Xase assay as described in Materials and Methods.