LTC-IC activity of CD34⁺CD38⁻and CD34⁺CD38⁺ cells in MDS cases with +8.

Six-week LTC-CFC activity of MDS BM CD34⁺CD38⁻(A) and CD34⁺CD38⁺ (B) cells was evaluated as described in “Patients, materials, and methods.” CD34⁺CD38⁻ and CD34⁺CD38⁺ cells from healthy subjects were included as controls in all experiments. After 6 weeks of culture, the number of CFCs produced was evaluated in methylcellulose. Results are the mean of 3-6 replicate wells from each cell population and patient. For patients #1 and #6 human allogeneic stroma was used while murine stromal feeders was used for patients #9, #10, #11, and #12. Note that the number of colonies found for the normal controls evaluated on human allogeneic stromas (patients #1 and #6) are significantly lower than those evaluated on murine stromal feeders (patients #9, #10, #11, and #12), reflecting the higher efficiency of the murine stromal feeders. Note also that no LTC-CFC activity was observed in the CD34⁺CD38⁺ populations of any MDS patient or in the CD34⁺CD38⁻ population from patients #1, #6, #9, and #10 and that the only 2 MDS patients with LTC-CFC activity derived from CD34⁺CD38⁻ population were those with most advanced MDS (RAEBt with 20% and 25% BM blasts, respectively).