Human erythroid cell reconstitution in bone marrow of humanized mice. Bone marrow cells were harvested from femur and tibia of humanized mice 18 weeks after human CD34⁺ FLC transplantation, and analyzed by flow cytometry and cytospin. (A-B) The levels of huCD45⁺ and huCD235a⁺ cells in the indicated regions were determined by flow cytometry. Shown are flow cytometric profiles (A) and levels (mean ± SD; n = 9) of human CD45⁺ cell chimerism (ie, percentage of huCD45⁺ cells in huCD45⁺ plus muCD45⁺ cells) and CD235a⁺ cell chimerism (ie, percentage of huCD235a⁺ cells in huCD235a⁺ plus Ter119⁺ cells) in the indicated regions (B). RBCs were mainly detected in R2 and R3, but not R4 (granulocyte region). ***P < .001. n.s. indicates not significant. (C-D) Human CD235⁺ cells (C) and mouse Ter119⁺ cells (D) in gated R2 region were purified from bone marrow by cell sorting and analyzed morphologically. The purity (ie, percentage of human CD235a or mouse Ter119 cells in the sorted cell population) and Wright Giemsa staining of the sorted cells are shown in left and right panels, respectively. (E) Representative flow cytometric profiles showing human CD71 expression on gated huCD235a⁺ cells in R2 and R3. MFI indicates median fluorescence intensity.