Relationship between cell proliferation and maintenance of LTC-IC function. Single G₀CD34⁺CD38^–/lo cells were delivered into individual round-bottomed 96-well plates prepared with complete medium and one of the 7 cytokine cocktails depicted on the x-axis (Table 1 presents details). On day 7, cells from 1776 individual wells were assayed for LTC-IC function as described in “Materials and methods.” Percentage of wells determined to have originated from an LTC-IC was plotted on the z-axis for all 7 cytokine combinations (x-axis) according to the size of the clone detected in each well (y-axis) on days 5 (A) and 7 (B). Cell numbers were grouped to represent 1 and 2 divisions (1-4 cells; yellow bars), 3 divisions (5-8 cells; red bars), and more than 3 divisions (> 8 cells; green bars). Between 100 and 428 clones were analyzed for each cytokine combination.