Treatment with human EPO and IL-3 promotes human erythropoiesis in macrophage-depleted humanized mice. Humanized mice were prepared by injection of human CD34⁺ FLCs into NOD/SCID mice after sublethal irradiation. At week 13, the mice were treated with clodronate liposomes (100 μL for the first injection and 50 μL every 5 days thereafter) plus human cytokines (EPO and IL-3; n = 4) or PBS (n = 6), or with human cytokines alone (EPO and IL-3; n = 4). EPO (30 U) and rhIL-3 (100 ng) were given every 3 days starting 1 day after the first injection of clodronate liposomes. (A) Flow cytometric profiles at week 4 after treatment. (B) Percentages (mean ± SEM) of human CD235a⁺ RBCs in blood at the indicated time points after treatment. *P < .05, for the indicated group compared with the other groups.