Analysis of gene transfer efficiencies.

Gene transfer efficiencies to CD34⁺ cells, CD34⁺CD38⁻ cells, CFC, and LTC-IC-derived CFC were obtained after prestimulation of CD34⁺CD38⁻ BM cells with FL + SF + IL-3 (open bars), FL + SF + IL-3 + HIL-6 (hatched bars), or FL + SF + IL-3 + HIL-6 + TPO (black bars) for various intervals followed by a single exposure to VCM. Gene transfer rates were assessed by FACS 48 hours after the first exposure of the cells to virus to determine the proportion of GFP⁺CD34⁺ or GFP⁺CD34⁺CD38⁻ cells, or by plating the cells directly, or after 6 weeks in LTC, in methylcellulose to measure the proportion of G418-resistant CFC and LTC-IC–derived CFC, respectively. Values shown are the mean ± SEM of data pooled from 3 independent experiments.