Effects of anti-fXII antibodies on plasma coagulation. (A) Results of a standard aPTT assay using a silica-based reagent for normal human plasma supplemented with different concentrations of IgG 9A2 (○) or 15H8 (●). Data are averages of 2 clotting times. (B) aPTT assay of normal human plasma supplemented with control vehicle (C), 4 μM 9A2 or 15H8, or 4 μM of both antibodies. Each circle represents a single clotting time, and the bar indicates the mean for the group. (C) aPTT results for human fXII-deficient plasma mixed with normal human (○) or baboon (●) plasma in various ratios. (D) Effect of different concentrations of IgG 15H8 on the aPTT of baboon plasma.