Flow cytometric analysis of bulk experiments. Since the amount of cells depicted in the plots is normalized to the cell number initially used, plots can be compared semiquantitatively. Cells analyzed in panels B and C were gated according to the morphology depicted on the forward scatter/side scatter plots shown in panel A. Plots in panel B represent the distribution of CD34 and CD133 antigens in freshly isolated or in expanded CD34⁺ cells, respectively. A characteristic isotype control of expanded cells is shown as inlet in the right panels. To identify the individual subpopulations in panels A or C, CD34⁺CD133⁺ cells are labeled in red, CD34⁺CD133^- cells in green, and CD34^-CD133^- cells in black. The PKH2 staining, representing the number of cell divisions single cells have performed, is plotted against the CD133 antigen distribution in panel C. PKH2^bright cells are plotted within the right quadrants of the diagrams shown in panel C. See “Results” for more details.