Efficient enucleation is observed after 10 days in differentiation medium. (A-C) Enucleated cells and nuclei were measured by flow cytometry, using DRAQ5 DNA staining against size (forward scatter) as shown in panel C. (A) The percentage of enucleated erythroid cells was measured during differentiation in culture dishes (closed symbols) and a G-Rex system (open symbols). Error bars indicate SD (n = 4). Comparisons were made by unpaired Student t test. (B) Ratio of nuclei vs cRBC during differentiation in culture dishes or G-Rex (<1 means more cRBC than nuclei). Mean ± SD (unpaired Student t test, *P < .05, **P < .01; n = 3-4). (C) Enucleation percentages of 10 days differentiated erythroid cultures before and after passage through a leukoreduction filter. Q1, nuclei; Q2, nucleated cells; Q3+Q4, enucleated cRBC. (D) Cytospins of the samples analyzed in panel C stained for hemoglobin with benzidine and general cytological stains. As comparison, cytospins of native peripheral blood erythrocytes are shown.