C/EBP-ϵ^32/30 enhancement of eosinophil differentiation does not require IL-5. CD34⁺ CB progenitors were transduced 3 times over a period of 72 hours with the retroviral vector encoding the C/EBP-ϵ³² activator isoform or empty vector control. CD34⁺GFP⁺ cells were sorted by FACS, and either plated in Collagen Cult colony assay media containing SCF and IL-3, and the cells allowed to differentiate for 14 days without (A) or with (B) IL-5 added to drive eosinophil colony formation. Eosinophil and GM colonies were enumerated using staining with Fast Green/Neutral Red and May-Grünwald Giemsa, respectively. The mean (± SD) number of CFU-Eos and CFU-GM colonies that developed from 750 CD34⁺GFP⁺ transduced progenitors is plotted for triplicate determinations (A,B).