Total cell numbers and progenitor levels in ex vivo-cultured CD34⁺ cells. CB CD34⁺enriched cells were cultured (2 × 10⁵ cells/0.5 mL) in RPMI + 10% FCS + 1% BSA or in serum-free media, both supplemented with cytokines, for 3 or 6 days. Cytokines were used in the following concentrations: SCF at 100 ng/mL, FL at 100 ng/mL, and IL6RIL6 chimera at 150 ng/mL. (A) Cells were counted for viable cell numbers. (B) Ex vivo-cultured cells were seeded (4 × 10³ cells/mL) into semisolid media, and colonies were scored on day 14. Progenitor levels were calculated on the basis of total cell numbers. Values shown are the mean ± SE from 10 independent experiments.