The flow cytometric assay for unlabeled and biotin-labeled F cells.

Cells were incubated with SA-PE, fixed, permeabilized, incubated with anti-HbF–FITC, and analyzed by 2-color flow cytometry. The percentage of labeled cells (B-RBCs) was consistent with values obtained in nonpermeabilized samples. F-cell analyses were gated on the unlabeled (non-B-RBCs) and labeled (B-RBCs) cells. Two time points are shown: 20 minutes, with the unlabeled and labeled cells having approximately the same percentage F cells (14.2% and 14.5%), and 8 days, with the unlabeled cells unchanged (14.9%) and the labeled cells increasing to 39.7%.