Flow cytometric analysis of lineage markers on human hematopoietic cells engrafted in NOD/SCID– ß₂m^–/– mice. CD34⁺ cells were expanded for 2 weeks on control stromal cells (panel A), or on Ihh stromal cells (panel B), and then transplanted into NOD/SCID–ß₂m^–/– mice. Hematopoietic cells were immunolabeled with a FITC-conjugated hCD45 antibody to ensure human origin, and with a PE-conjugated antibody specific for the indicated lineage marker. Data shown are from 1 representative experiment of 4 showing similar results. Numbers in each quadrant indicate percentages of hematopoietic cells.