Coexpression of different markers with CD99 within the mPB CD34⁺ cell subset. (A) CD99 expression levels increase simultaneously with Thy1, CD105, and AC133. Conversely, levels of CD38, nectin1 (CD111), c-Kit, and CXCR4 tend to decrease, whereas levels of CD99 increase. The rare ABCG2⁺ cells express high levels of CD99. For each antigen, values in the dot plots represent the ratio of MFI for this specific marker in the CD34⁺/CD99^high population versus the CD34⁺/CD99^low population, as defined in Figure 1B (data are mean ± SEM of 9 experiments). Due to the low percentage of ABCG2⁺ cells, this value was not computed for this marker. (B) A representative experiment showing detection of ALDH activity in total CD34⁺ cells and gated CD34⁺/CD99^low and CD34⁺/CD99^high cells. (i) Aldefluor-stained CD34⁺ cells incubated with DEAB, a specific ALDH inhibitor; (ii) total CD34⁺ cells incubated with Aldefluor, analysis of Aldefluor-positive cells gated on (iii) CD34⁺/CD99^low cells and (iv) CD34⁺/CD99^high cells.