Expression of SCF receptor (CD117), transferrin receptor (CD71), and GPA during the 14-day culture period.

On every third day in erythroid culture (indicated at left), cells were sampled and stained with fluorescent-labeled antibodies and analyzed by flow cytometry. Each panel shows distribution of antibody binding (fluorescence; y-axis) versus the forward scatter (cell size; x-axis). The horizontal lines demonstrate the upper level of cellular autofluorescence plus the signals from isotypic control antibodies. The percentage of cells with fluorescence above the isotypic controls is shown in the upper right corner of each panel. Arrows show populations with high-level CD117 expression on days 6 and 9. Bottom panels show mean percentages of positive cells with SE bars from separate experiments performed on the cells of 3 donors.