Flow cytometric analysis of HbF and HbA.

Distributions of fluorescence versus size for cells stained with isotypic control antibodies (control) versus antibodies directed against HbF and HbA (stained separately) are shown according to the culture day on the left. The level of fluorescence demonstrated by at least 95% of the control-stained population (horizontal bars) was used to define the positive population. The percentage of hemoglobin-stained cells with fluorescence above that level is shown on the upper right of each panel. Nearly identical staining was detected with isotypic control antibodies for HbF and HbA; the HbF control panels are shown.