Growth and death of erythroid cells. On day 4, equal numbers of untransduced (CTRL) and transduced (EF1 GFP or EF1 IK6) erythroid cells were replated in erythroid conditions. (A) On days 10, 13, 17, and 20, living untransduced and transduced erythroid cells derived from CB CD34⁺ cells were counted with trypan blue dye exclusion. The mean cumulative cell numbers of 7 experiments (± SEM) are shown. *P < .05 using the Wilcoxon test compared with CTRL and EF1 GFP conditions. (B) In erythroid culture of CB CD34⁺ cells, percentage of dead cells was determined on days 10, 13, 17, and 20 using an annexin V assay (mean values ± SEM for 7 independent experiments).