Representative FACS profiles of CFSE-stained cord blood cells before (A) and after (B and C) culture for 5 days in the presence of IL-3, IL-6, SCF, G-CSF, and FL. The initial sort gate used to isolate the cells placed in culture is indicated in (A). The arrows in (B) and (C) indicate the persisting undivided cells identified by comparison to a control aliquot of the cells cultured under the same conditions but in the presence of colcemid to suppress cell division. The profile shown in (C) was derived by gating on the highly fluorescent (CFSE⁺) cells to allow a better discrimination of the undivided population.