HMOX-1^–/– HIS mice have hRBCs in peripheral blood. HMOX-1^–/– and HMOX-1^+/+ MSRG47 mice were intrahepatically engrafted with hHSCs. At 12 weeks after engraftment, mice were examined for (A) total circulating hCD45⁺ cells (human leukocytes) in the peripheral blood and BM. (B) Total RBC levels in the blood of nonengrafted vs engrafted HMOX-1^+/+ and HMOX-1^–/– mice. (C) Levels of human CD3⁺ T cells, CD19⁺ B cells, NKp46⁺ NK cells, and CD14⁺ myeloid cells (as percentage of total hCD45⁺ cells) are shown in the blood. (D) Levels of human CD3⁺ T cells, CD19⁺ B cells, NKp46⁺ NK cells, and CD14⁺ myeloid cells (as percentage of total hCD45⁺ cells) are shown in the BM. HMOX-1^+/+ compared with HMOX-1^–/–: T cells, no significant difference; blood B cells, P = .006; BM B cells, P = .0005; blood NK cells, no significant difference; BM NK cells, P = .0059; blood myeloid cells, P = .03; and BM myeloid cells, P = .01. (E) Number of hRBCs per microliter of blood of HMOX-1^+/+ and HSC donor-matched HMOX-1^–/– HIS mice. At least 7 independent experiments were performed. (F) Total number of hRBCs in the BM of HMOX-1^+/+ and HSC donor-matched HMOX-1^–/– HIS mice is shown. Data represent the mean ± standard error of the mean (SEM) with individual mice shown. Statistical analysis was evaluated by unpaired Student t test. Experimental analysis was performed at least 3 times, with representative analysis shown.