Sorting of p14⁺ and p14⁻cells present after long-term culture with FLT3-L plus TPO. Ex vivo–sorted CD34⁺ cord blood cells were grown for 21 days in FLT3-L plus TPO, with an increase in total cell number of 110-fold and were frozen. Cells were thawed 3 months later and grown for 26 extra days in the same conditions, with an increase in total cell number of 12-fold, giving an overall proliferation of 1,320-fold. Cells were then sorted in either CD1a⁻CD14⁺CD34⁻(p14⁺) or CD1a⁻CD14⁻CD34⁻(p14⁻) with a cocktail of anti–CD1a-PE, anti–CD34-PE, and anti–CD14-FITC MoAbs and cultured for 3 days with GM-CSF and IL-4, GM-CSF, IL-4, and TNF or for 3 and 9 days with GM-CSF and TNF. These data are from one experiment representative of seven. Sorting cells from primary cultures at different time points produced similar results.