Maintenance of human CD34⁺CD38⁻ cells in serum-free cultures initiated with CB cells enriched for CD34⁺ cells. The number of total cells (⧫), CD34⁺ cells (▪), and CD34⁺CD38⁻ cells (•) are shown as a function of time in culture. To calculate the number of CD34⁺ cells or CD34⁺CD38⁻cells at each time point, the number of total live cells (counted with a hemocytometer) was multiplied by the percentage of CD34⁺ cells or CD34⁺CD38⁻cells obtained by FACS. Shown is a representative figure of one of three experiments.