Expansion of total and CD34⁺ cell number in sequential harvest cultures. Sorted CD34⁺CD38⁻Lin⁻ cells were cultured in medium supplemented with cytokines and harvested after different culture periods as indicated. Points represent average expansion (fold increase of start cell number) of all cells (A) or CD34⁺ cells (B) from independent experiments with 3 different donors, error bars indicate SD. (▪) TPO + FL, (□) TPO + FL + SCF, (⧫) IL-3 + SCF, (◊) IL-3 + SCF + IL-6.