Experimental design of ex vivo expansion of LTC-IC and ELTC-IC. CD34⁺CD38⁻ BM cells (BMC; maximum 1,000 cells/mL) were cultured in SF medium supplemented with cytokines. After 7 or 12 days of expansion culture, cells were counted and transferred to either 5- or 12-week LTC. At the end of the 5 or 12 weeks of stroma coculture (no cytokines added), LTC-IC–derived CFC (LTC-CFC) were detected in a CFC assay.