Comparison of survival of donor RBCs derived from littermate control (NF-E2^+/+), knockout (KO) or wild-type Swiss Webster (SW) adult mice, labeled with fluorochrome, and measured for approximately 1 month after intravenous administration into recipient SW or NF-E2^+/+ mice. Data are expressed as the percentage of labeled cells detected at various time points relative to the maximum number of cells detected 2 hours after injection.