(A) Nonadherent cell expansion from CD34⁺ CB cells. Two thousand CB cells in 1 mL were plated in quadruplicate 24-well plates on day 0. Cells were cultured in stroma-free in LTC medium in the presence of FL, KL, IL-3, and IL-6 alone or combined. Every week half the culture volume was removed from cell culture and the cells were counted. The mean fold increase over cell number plated on day 0 is shown at each time point of LTC. Mean ± SEM from three separate experiments performed in quadruplicate. (B) CFU-GM expansion from CD34⁺ CB cells in stroma-free LTC. Two thousand CD34⁺ CB cells were plated in quadruplicate 24-well plates in the presence of the factors reported above. The content of CFU-GM of each well was established at the beginning of the LTC by agar assays. Every week all the wells were demidepopulated by removal of one half the culture volume, which was replaced with freshly medium and growth factors. Cells of the harvested media were counted and suitable aliquots of the cell suspension were assayed for CFU-GM in quadruplicate dishes. The results represent the mean ± SEM of three separate experiments performed in quadruplicate. (▴) IL-3 + FL; (▵) IL-3 + KL; (•) IL-3 + KL + FL; (□) IL-6 + FL + KL; (▪) KL + FL.