Bone marrow (BM) and cord blood (CB) CD34⁺ cells were cultured in parallel and expanded in IMDM supplemented with 20% FCS, c-kit-ligand, fit-3 ligand, GM-CSF, and TNFα for 12 days. Retroviral transduction was performed during day 3 of CD34⁺ expansion by coculture with mCD2 encoding ψ-Crip retroviral producers. Cytofluorographic analysis of day-12 nonadherent progeny was performed by dual staining with FITC-conjugated rat antimouse-CD2 and the indicated PE-conjugated test antibodies. All events in both FITC (FL1) and PE (FL2) channels were recorded and analyzed for log₁₀ fluorescence. The mean fluorescence index (MFI) in the PE channel was calculated by the Consort 30 software (Hewlett Packard) after quadrants were set according to background staining by isotype controls.