HPC^LSKcell lines can repopulate the hematopoietic system. (A) Experimental scheme: Ly5.1⁺-recipient mice were lethally irradiated (10 Gy) 24 hours prior to IV injection of 1 × 10⁷ Ly5.2⁺ BM (positive control), BM-HPC5, or HPC^LSK cells. Forty days later, some mice of the BM and HPC^LSK-injected group were euthanized, and hematopoietic organs were analyzed. The remaining injected mice were analyzed for their long-term survival. (B) Survival of BM- (n = 7), BM-HPC5- (n = 8), and HPC^LSKs- (n = 10) injected mice compared with radiation control (n = 9), log-rank (Mantel-Cox) test. ***P <.0001. (C) WBCs and red blood cells in peripheral blood of BM- and HPC^LSK-injected recipients were compared 40 days after treatment. Data are presented as mean ± standard error of the mean (SEM; *P <.01, Student t test or Mann-Whitney test for platelets) in 6 to 12 mice per group. (D) Comparison of Ly5.2⁺ BM vs HPC^LSK cells’ engraftment in the blood, BM, spleen, and thymus of lethally irradiated Ly5.1⁺ mice after 40 days. Data are presented as mean ± SD, n ≥ 4. (E) Spleen weights of mice 40 days after lethal irradiation and BM or HPC^LSK injection. Data represent mean ± SD, n ≥ 5. (F) Composition of the engrafted Ly5.2⁺ HPC^LSK cells in blood, BM, and thymus after 40 days. ST-HSC, MPP (Lin⁻, Sca-1⁺, c-Kit⁺, CD150⁻, CD48⁺), LSKs (Lin⁻, Sca-1⁺, c-Kit⁺), MCP (myeloid committed progenitor, Lin⁻, IL-7R⁻, Sca-1⁻, c-Kit⁺), GMP (granulocyte-monocyte progenitor, Lin⁻, IL-7R⁻, Sca-1⁻, c-Kit⁺, CD16/32⁺, CD34⁺), CMP (common myeloid progenitor, Lin⁻, IL-7R⁻, Sca-1⁻, c-Kit⁺, CD16/32⁻, CD34⁺), MEP (megakaryocyte-erythrocyte progenitor, Lin⁻, IL-7R⁻, Sca-1⁻, c-Kit⁺, CD16/32⁻, CD34⁻), CLP (common lymphoid progenitor, Lin⁻, IL7-R⁺, c-Kit^mid, Sca-1^mid); and in vivo differentiated populations: erythroblast (CD71/CD44⁺), granulocyte (Gr-1⁺), monocyte (CD11b⁺), eosinophil/neutrophil (Gr-1/CD11b⁺), T cell (CD4 or CD8⁺), and B cell (B220⁺) are depicted as fold change compared with BM-injected mice. n = 6 to 12 per group, *P <.05; **P <.01; ***P <.001 by Student t test. Ctrl, control; inj., injected; ns, not significant; rad, radiation; RBC, red blood cell.