PS is exposed on a subpopulation of murine sickle cells.

Murine RBCs were labeled with fluorescent annexin V and analyzed by flow cytometry. Average of 11 sickle mouse samples (SS RBC) and 19 control samples (WT RBC) are indicated. To assess the percentage of annexin V–binding reticulocytes, the cells were double- labeled with biotin–annexin V–PE-streptavidin and thiazole orange to indicate the presence of RNA. Averages of 8 sickle mouse samples (SS retic) and 9 control samples (WT retic), subgroups of the annexin V–labeled samples, are indicated.