Sequential dilution expansion (Delta assay) of AdGFP-infected CD34⁺ cells in the presence of IL-3, IL-6, G-CSF, KL, and EPO. Increasing concentrations of AdGFP (MOI of 0 to 1,000) used for infection of CD34⁺ cells before expansion did not impair the proliferative capacity of the cells. In all conditions, the cells cumulatively expanded by 3 log. The cumulative number of GFP-expressing progeny derived from AdGFP-infected CD34⁺ cells was measured throughout the expansion culture. If MOIs >100 were used for infection of CD34⁺cells, moderate expansion (1 log) of GFP⁺ progeny was observed. However, with lower MOIs (<100) used for infection, the number of GFP⁺ progeny did not proportionally increase during expansion.