mAb-RC3 inhibits human thrombus formation independent of PAR4 variant expression. (A) Representative 3-dimensional reconstructions and (B-E) quantitation of human thrombi formed after 3 minutes of a whole blood thrombosis assay, showing platelets (red, anti-CD9), thrombin (green, thrombin probe), and fibrin (purple, anti-fibrin). (B,C) Pretreatment of blood with mAb-RC3 (RC3, 100 μg/mL) significantly inhibited fibrin formation, but the effect on platelet deposition did not reach significance. (D) This translated to a significant reduction in total thrombus volume. Individual data points are shown. Bars are mean ± standard error of the mean of all N = 18 experiments. *P < .05; not significant (ns) (unpaired Student t test). (E) Pairwise analysis for all individuals, separated by PAR4 genotype, showing a reduction in total thrombus volume in all individuals except the 2 with the lowest baseline response.