FACS analyses and hemoglobin (Hb) staining of splenocytes from naive or P chabaudi AS–infected mice, either untreated or treated with 10 units of rmEPO per day for 3 days. The erythroblast population was identified with PE-conjugated anti-TER119 antibody (A-D). Region M1 represents gating for TER119⁺ cells. Terminally differentiated mature erythroblasts were identified with benzidine staining for the presence of Hb as described in “Materials and methods” (E-H). Data presented are naive mice (A,E), naive mice treated with EPO (B,F), infected mice (C,G), and infected mice treated with EPO (D,H). Values represent percentages of TER119⁺ (A-D) or Hb-positive cells (E-H). Data are expressed as means ± SEM for 3 to 5 mice per group. When 2 sets of data are labeled with superscripts of different lowercase letters, it indicates that these 2 sets of data are statisitcally different (P < .05). Similar results were obtained in 3 independent experiments. Photos were taken at × 200 magnification.