In vitro inhibition of fVIII by MAbs 2-76, 2-54, and 1D4. fVIII was reconstituted into fVIII-deficient plasma at 1 U/mL, and the inhibition of fVIII by MAbs 2-76, 2-54, and 1D4 was measured by (A) chromogenic assay and (B) 1-stage coagulation assay. The curves represent 4-parameter logistic fits to the data. (C) The effect of high-dose thrombin on the cleavage of fVIII in the presence of MAb 2-54. Standards represent 250, 150, 100, 75, 50, 37, 25, 20, 15, and 10 kD. LC, light chain; LC IIA, thrombin-activated LC.