CFU during transduction and expansion periods. For each animal, the total CFU (CFU-GM, CFU-M, CFU-G, and BFU-E) present in the cultures at the following time points are shown: starting CD34 enriched fraction (Starting), the end of transduction for the nonexpanded fraction (End Transduction-NE), the end of transduction for subsequently expanded fraction (End Transduction-Exp), and the end of expansion (End Expansion). The culture conditions are shown below: IL-3, interleukin-3; IL-6, interleukin-6; SCF, stem cell factor; FLT, flt3 ligand; STR, autologous stromal monolayer.