Human RBCs reconstitute in humanized mice after macrophage depletion. Humanized NOD/SCID mice were treated at 13 weeks after human CD34⁺ FLC transplantation with clodronate liposomes (n = 6) or PBS liposomes (n = 3; 100 μL at days 0, 2, 7, 12, 17, and 22). In clodronate liposome-treated group, 4 mice died after treatment, and the number of mice available for analysis were: n = 6 for pretreatment, n = 4 for weeks 1 and 2, n = 3 for weeks 3 and 4, and n = 2 for weeks 5 and 6. Blood was collected 1 week before and weekly after clodronate liposome treatment, and the percentages of human RBCs were determined by flow cytometry. (A) Representative flow cytometric profiles at week 3 after treatment. (B) Percentages of human CD235a⁺ RBCs in blood at the indicated time points after treatment. Arrow indicates the time we stopped treatment. (C) Human CD235⁺ cells were purified by cell sorting from blood of macrophage-depleted humanized mice and analyzed by flow cytometry and cytospin. Shown are flow cytometric profiles of human CD235a and CD71 expression and Wright Giemsa staining of the purified cells. (D) Percentages (mean ± SD) and representative staining profiles of human CD71 expression on gated human CD235a⁺ cells in the “mature erythrocyte–enriched” R2 region of bone marrow cells (as defined in Figure 2A) from humanized mice treated with PBS liposomes (n = 3) or clodronate liposomes (n = 3).