Effect of individual histones on prothrombin cleavage and thrombin generation. (A) Coomassie blue–stained gel shows the cleavage of prothrombin by FXa in the presence of individual histones after 60-minute incubation with calcium (5 mmol/L) at 37°C. (B) Densitometric quantification of the percentage of prothrombin digested over time. Mean curves from 3 independent experiments are shown. (C) Thrombin generation from FXa activation of prothrombin in the presence of individual histones and calcium (5 mmol/L) with typical curves from 3 independent experiments. (D) Mean ± SD of relative thrombin generation from 3 independent experiments. *P < .05 (Student t test) compared with that in the absence of histones. (E) Prothrombin cleavage by FXa in the presence of H3 or H4 without or with ahscFv (100 µg/mL) or heparin (6 µmol/L) following 60-minute incubation with calcium (5 mmol/L) at 37°C. Percentages were calculated from Coomassie blue–stained gels from 3 independent experiments (mean ± SD). Student t test shows significant increase compared with prothrombin + FXa alone untreated by histones (UT, red) (*P < .05). A significant reduction (^#P < .05) was found when comparing prothrombin cleavage in the absence or presence of anti-histone reagents to histones alone. (F) The effects of ahscFv and heparin on thrombin generation presented as mean ± SD of thrombin (nmol/L). Student t test shows a significant increase compared with prothrombin + FXa alone untreated by histones (UT, red) (*P < .05). A significant reduction (^#P < .05) was found when comparing thrombin in the absence or presence of antihistone reagents to histones alone.