fVIII functional assays in the presence of group A, AB, and B anti-C1 mAbs. (A) Inhibition of fVIII procoagulant activity by type 2 group A mAb I84 (^●), type 1 group AB mAb KM33 (▪), and type 1 group B mAb B136 (△) by Bethesda assay. (B) Inhibition of fVIII binding to PCPS and (C) fVIII binding to VWF in the presence of anti-C1 mAbs group A B153 (^●), group AB KM33 (▪), and group B B136 (△) determined by competitive ELISAs.