Distribution of cells produced by CD34⁺CD38^low cells in 4 days according to their proliferation rate.

CD34⁺CD38^low cells labeled with CFSE and cultured for 4 days in the presence (black bars) or in the absence (stippled bars) of MS5 cells (as described in the Figure 1 legend and “Materials and methods”) were analyzed by FACS. Each histogram represents the mean (± SEM, n = 5-8) proportion of day 4 cells that fell in the peak corresponding to 0, 1, 2, 3, 4, 5, or 6 divisions (Figure 1). There were no significant differences in the proportions of cells that accomplished a given number of cell divisions with or without MS5 cells (P > .5).