Analysis of human genome and the percentage of hCD45 in NOD/SCID–ß₂m^–/– mice. Analysis of human genome and the percentage of hCD45 in NOD/SCID–ß₂m^–/– mice. (A) PCR amplification of human ALU sequences was performed to confirm the sequence found in the human genome. Mice (n = 3) with transplants of accessory cells only (lanes 1-3); mice (n = 5) with transplants of fresh CD34⁺ cells (lanes 4-7). The percentage of hCD45 indicates the percentage of the human CD45⁺ hematopoietic cells in the BM of mice with transplants. (B) Analyses of hCD45⁺ cells in the BM of NOD/SCID–ß₂m^–/– mice with transplants. Irradiated carrier cells, fresh CD34⁺ cells, or CD34⁺ cells that had been expanded on control stromal cells or Ihh stromal cells, were transplanted into NOD/SCID–ß₂m^–/– mice. Mice were killed 8 weeks after transplantation, and the BM cells were analyzed by flow cytometry. Data are shown for carrier cells; fresh CD34⁺ cells; CD34⁺ cells that had been expanded ex vivo in the absence of stromal cells for 2 weeks; CD34⁺ cells that had been expanded on control stromal cells for 2 weeks; CD34⁺ cells that had been expanded on control stromal cells for 2 weeks in the presence of anti-Ihh blocking Ab; CD34⁺ cells that had been expanded on Ihh stromal cells for 2 weeks; and CD34⁺ cells that had been expanded on Ihh stromal cells for 2 weeks in the presence of anti-Ihh blocking Ab. A dotted line indicates the cut-off level (0.1%) for successful engraftment of human hematopoietic cells. *P < .05 versus control stromal cells. **P < .05 versus Ihh stromal cells (Mann-Whitney U test). Data represent a summary of 2 separate experiments. (C) Engraftment of a graded dose of CD34⁺ cells at the start of culture and their progeny after 2 weeks. Percentage of engraftment of human CD45⁺ cells that had been expanded with control stromal cells (i), or Ihh stromal cells (ii) is shown. Dotted lines indicate cutoff level (0.1%).