Antibodies binding ERFE N-terminal domain block hepcidin suppression in EPO-treated mice. Eight-week-old wild-type male mice were treated intraperitoneally with 200 IU of EPO in combination with intravenous injection of an IgG2A antibody control, anti-ERFE 15.1, or anti-ERFE 20.1 (or vehicle alone instead of EPO for analysis of baseline values). Mice were killed and analyzed 18 hours after treatment for assessment of Hamp expression (A) and serum hepcidin (B). n = 3, vehicle; n = 5-6, EPO-treated mice. *P < .05; **P < .01; ***P < .001; ****P < .0001 using the Student t test.