Flow cytometric analysis of erythroblasts stained with a specific anti-HbF fluoresceinated monoclonal antibody. Peripheral blood mononuclear cells from a healthy individual were cultured in the presence of increasing concentrations of SW68. At day 14 of culture, BFUe-derived colonies were collected and stained with a specific PE-conjugated anti-HbF antibody, and the percentage of HbF-positive erythroblasts was determined. Notice the consistent increase of HbF-positive erythroblasts as the concentration of the compound increases in culture. Solid lines indicate results obtained in cultures done in the presence of SW68. Gray area represents the baseline measurements in a BFUe culture done in the absence of SW68.