Flow cytometric analysis of GFP and CD24 expression in BM cells transduced with either the MGirL22Y vector or the CD24 vector. (A) Evaluation of GFP expression in BM cells 24 hours after completion of the transduction period. The broken line indicates the fluorescence profile of unstained, CD24-transduced control marrow while the solid line indicates the fluorescence profile of the GFP-transduced marrow. The extremely high level of fluorescence of the GFP-expressing cells necessitated the use of lower fluorescence amplification when analyzing for GFP expression. The proportion of positive cells in the population as well as the population expressing high levels of GFP that was FACS purified is shown. (B) Evaluation of CD24 expression in BM cells 24 hours after completion of the transduction period. The broken line indicates the fluorescence profile of GFP-transduced control marrow stained with an anti-CD24 antibody while the solid line indicates the fluorescence profile of the CD24-transduced marrow. The proportion of positive cells in the CD24-transduced population is shown.