Protection of ES-MDS erythroid precursors from death by FADDdn. (A) Diagram of the FADDdn mutant lacking amino acids 1-80 in the DED of FADDwt. (B) Flow cytometry analysis of annexin V-PE-labeled ES-MDS erythroid precursors treated with 500 ng/mL of the agonistic antibody to Fas (CH11) or of irrelevant IgM on cultures at day 10. The percentages of annexin V-positive cells are indicated. (C) Caspase-8 activity (AU) in FADDdn and EGFP-transduced ES-MDS (n = 5; ▪) and healthy control (n = 4; □) erythroid precursors on culture day 14. (D) Cell death on days 7 and 14 after transduction with EGFP (□) or FADDdn (▦) expressed as mean percentages of annexin V-PE⁺ cells (± SEM; ^**P < .005).