KL-driven generation of wasp^+/− BMMCs reveals a selective advantage for WASP-expressing cells. In 2 separate experiments that delivered corresponding results (1 shown), 3 cultures from wasp^+/− BM were established at day 0 and maintained in the presence of KL as growth factor (40 ng/mL) for 90 days. Intracellular WASP expression was evaluated in the Kit-positive populations of the wasp^+/− cultures (blue) and compared with that of the control wt (green) or wasp^−/− (red) cultures by flow cytometry at the culture days indicated.