Detection of human cell repopulation in mice that received transplants of purified ALDH^hiCD133^-Lin^-, ALDHhiCD133⁺Lin^-, or ALDHhiLin^- cells. Representative flow cytometric analysis of NOD/SCID β2M-null mice that received transplants of (A-C) 2 × 10⁵ ALDH^hiCD133^-Lin^-, (D-F) 10⁴ ALDH^hiCD133⁺Lin^-, or (G-I) 10⁴ ALDHhiLin^- cells. At 7 to 8 weeks after transplantation, human hematopoietic cells in the mouse BM were detected by coexpression of CD45 (R1) with CD38 (R2). Cell suspensions from murine spleen and peripheral blood were analyzed in an identical fashion. Injection of more than 2 × 10⁵ ALDH^hiCD133^-Lin^- cells was required to observe human cell engraftment in the BM of NOD/SCID β2M-null mice (n = 3). Mice that received transplants of 10⁴ ALDH^hiCD133⁺Lin^- cells showed enhanced engraftment with human cells (18.2% ± 10.9%, n = 6) in the murine BM, compared with mice that received transplants of 10⁴ ALDHhiLin^- cells not selected for CD133 expression (5.2% ± 1.7%, n = 5).