Transfusion of hpx mice with wild-type RBCs. Hpx mice were transfused with 0.5 mL PBS or washed wild-type RBCs every other day for 1 week then harvested on day 7 and analyzed for hemoglobin levels (A), reticulocyte counts (B), spleen masses (C), splenic Gdf15 levels (D), and hepatic Bmp6 (E) and hepcidin (F) levels. Gene expression levels were measured by QPCR and expressed as a ratio to β-actin levels. A ‘*’ indicates statistical significance (t test, P < .05) relative to values for PBS-transfused hpx mice.