Synergistic effect between 5B9 and 1E12 on TF synthesis and thrombus formation in vitro. (A) Relative TF mRNA synthesis after addition of 5B9 and/or 1E12 or UFH to whole blood from healthy donors (mean ± standard error of the mean [SEM], n = 6 donors). (B) Representative images of thrombus formation in von Willebrand factor–coated microfluidic channels perfused (8 minutes, 500 s^–1) with recalcified whole blood incubated with 5B9 and/or 1E12 with or without control Ab or UFH. Images corresponding to areas of 0.1 mm² are shown with platelets in green (DiOC6), fibrin(ogen) in red (Alexa Fluor 647–labeled fibrinogen), and leukocytes in blue (Hoechst 33342, DNA dye). (C) The mean areas covered by platelets (green), leukocytes (blue), or fibrin(ogen) (red) were calculated for each condition (mean ± SEM; n = 12 independent experiments), by measuring using ImageJ software the surface covered by large aggregates (>100 μm²) in 30 different areas. For each experiment, the highest concentration of 5B9 and 1E12 that did not induce thrombus formation when incubated alone in the absence of UFH was selected (50 or 100 μg/mL for 5B9 and 1 or 2 μg/mL for 1E12) and used for subsequent synergy experiments. Mann-Whitney U test was performed to compare the different conditions tested. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. IVIg, IV immunoglobulins.