Effect of wild-type fXI construct amount on fXI expression. The 293 fibroblasts were transfected with different amounts of wild-type fXI/pJVCMV expression construct as described in “Materials and methods.” For concentrations between 0.001 and 1 μg the total amount of DNA transfected was brought up to 2 μg with empty pJVCMV vector. Results are relative concentrations of fXI in media 67 hours after transfection compared with the mean for the 0.1 μg transfection, which was assigned a value of 100%. Results are means and standard deviations for 3 separate transfections, each tested in triplicate by ELISA. All results are corrected for transfection efficiency using a Renilla luciferase assay.