3E8 anti-HK antibody disassembles PK/HK and FXI/HK complexes in NHP in the absence of contact system activator ex vivo. NHP was incubated with PBS, 3E8, or hamster IgG at 37°C for 20 minutes. B-2B7 anti-HK antibody was added and incubated for an additional 20 minutes. Streptavidin was used to pull down B-2B7-bound proteins. (A) Representative western blot results of the pulldown experiments. While HK was pulled down in all samples, FXI and PK were only pulled down in PBS- or IgG-treated plasma (lanes 1 and 3 vs lane 2). (B) 3E8 anti-HK antibody pulled down significantly more intact HK than PBS/IgG samples. (C-D) FXI and PK were pulled down from PBS- and hamster IgG-treated, but not 3E8-treated NHP, indicating that 3E8 anti-HK antibody is able to disassemble PK/HK and FXI/HK complexes in normal human plasma in the absence of a contact system activator ex vivo. FXII and human albumin were not pulled down in any of the samples. n = 8 per group. Data are denoted as mean ± SEM. **P ≤ .01, ****P ≤ .0001.