Phenotypic analysis of purified ALDH^hiLin^- and ALDH^loLin^- populations. Human UCB Lin^- cells were analyzed by flow cytometry for ALDH expression in combination with the expression of primitive hematopoietic markers. (A-B) Lin^- cells were incubated with Aldefluor and an inhibitor of ALDH (DEAB) or with Aldefluor alone to establish R1 and R2 gates for ALDH^loLin^- and ALDH^hiLin^- cells, respectively. (C-D) ALDH^hiLin^- and ALDH^loLin^- populations were subsequently analyzed for the expression of CD34 with CD38. The frequency of CD34⁺CD38^- cells (R3) was greater in the ALDH^hiLin^- cells than in the ALDH^loLin^- cells (P < .05). (E-F) ALDH^hiLin^- and ALDH^loLin^- cells were also analyzed for the coexpression of CD34 with CD133. The frequency of CD34⁺CD133⁺ cells (R4) was increased in the ALDH^hiLin^- cells compared with the ALDH^loLin^- cells (P < .001). These data represent the mean ± SEM on experiments performed with Lin^- cells isolated from 6 UCB donors (n = 6). Numbers represent the frequency of events in the boxes.