STAT1-deficient erythroblasts have a higher rate of intrinsic apoptosis. Bone marrow and spleen cells from wild-type and STAT1^–/– mice were isolated and stained as described in Figure 3. Cells were then incubated with annexin V–FITC and propidium iodide. Ter119⁺ cells were gated and annexin V staining is shown as a function of CD71 expression. The analysis was completed for 3 wild-type and 3 STAT1^–/– mice. Percentage of annexin V⁺ cells is shown ± SE (*P < .005; **P < .05).