FeCl₃ carotid artery injury model. (A) The percentage of animals with FeCl₃-induced carotid injury that developed a stable occlusive thrombus (▪), transient occlusive thrombus (▦), and no occlusive thrombus are shown. The animals are arranged from no PF4 expression on the left to excess PF4 expression on the right. The number tested of each phenotype is indicated at the bottom (P < .005 mPF4^+/– versus mPF4^+/+; P < .0001 for mPF4^–/– versus mPF4^+/+ and hPF4⁺ versus mPF4^+/+). (B) Mean thrombosis score of wild-type and littermate mPF4^–/– mice treated with increasing doses of recombinant hPF4 infusion (n = 5 animals at each point). A thrombosis score of 2 = stable occlusive thrombus, 1 = transient occlusive thrombus, and 0 = no occlusive thrombus developed. The zero concentration data points are extrapolated from panel A. Numbers indicate levels of heparin infusion in which occlusive thrombi occurred at a significantly different rate from non–heparin-treated mice of that phenotype (P < .01, Student t test; 1 = mPF4^+/+, and 2 = mPF4^–/–).