Inhibition of the KKO-induced platelet accretion. (A) Microfluidic study of platelet accretion performed as in Figure 1 using blood from the double transgenic hPF4⁺/FcγRIIA⁺ mice and control hPF4⁺ mice after blocking TF activity induced by KKO with 1H1 antibody. Mean ± 1 SEM is shown. Relative platelet accumulation is expressed as the ratio calculated from AUC of percent area covered by platelets (AUC of sample inhibited by 1H1/AUC of sample incubated with isotype control). Dotted line represents no inhibition of stimulation by KKO. 1H1 inhibited and isotype control samples were run in parallel, and the significance of the difference was determined using paired two-tailed Student t tests. N = 6 for double transgenic mice and N = 3 for the single transgenic mice. (B) Effect of PPACK inhibition of thrombin activity on platelet accretion in human whole blood was measured following activation with KKO or the anti-PF4 antibody RTO that does not activate platelets. All samples were run in parallel and data are expressed as in (A), as the ratio of PPACK-treated to vehicle control sample. N = 3 with each experiment performed in duplicate.