Expression of R333Q-hFIX. The concentrations of R333Q-hFIX in homozygous (H/H), hemizygous (H/Y), heterozygous (H/+), and wild-type (WT) mice are shown in μg/mL as assayed by ELISA using paired anti-hFIX polyclonal antibodies. The levels are homozygous, 1.1 ± 0.1 μg/mL (n = 4); hemizygous, 1.3 ± 0.1 μg/mL (n = 3); heterozygous, 0.3 ± 0.1 μg/mL (n = 6). Wild-type mouse factor IX is not detectable with this antibody. Data represent the mean ± SD.