NOD/SCID-repopulating cells (SRCs) are enriched within the CD34⁺BB9⁺ subpopulation. Groups of mice received a transplant of CD34⁺ (▲), CD34⁺BB9⁺ (●), or CD34⁺BB9⁻ cells (○) at the doses shown. Shown are the levels of human engraftment assessed by flow cytometric analysis of the bone marrow at week 10 after engraftment using anti-hCD45. The mean percentage of hCD45 in each group is indicated.