Effect of fibrinogen γ′ peptides on the APTT-based APC response in normal and FV Leiden heterozygous plasma. APC resistance was measured with the APTT-based assay in normal (A) and FV Leiden heterozygous (B) plasma supplemented with 0 to 100 μM WT-S12 or SCR-S12 peptide. APCsr were plotted as a function of the peptide concentration. All clotting times were measured in triplicate. Error bars indicate the standard error of the mean.