CFSE dilution and annexin V binding of CD4⁺CD25⁻ T cells isolated from spleens of lethally irradiated B10.BR recipients injected with 10⁷ BM and 5 × 10⁶ CFSE-labeled CD4⁺CD25⁺ T cells from WT or Stat5b-CA TG mice. (A) Splenocytes were isolated on day 3 (left) and day 5 (right) after transplantation, and donor H-2K^b+CD4⁺ T cells were analyzed for CFSE dilution (illustrated in top and bottom panels) and annexin V (illustrated in top panels) expression. Representative flow cytometry data from one of 6 mice/group from 2 separate experiments are shown. Responder frequency (B) and proliferation index (C) were calculated. (D) Total cell numbers harvested from spleen on day 3 and day 5 from recipients described in panel A. (E) Survival of lethally irradiated B10.BR recipients of 10⁷ BM (*) and 1 × 10⁶ B6 CD4⁺CD25⁻ T cells isolated from WT (▼) or Stat5b-CA TG (▽) mice or a mixture of both (●). P = not significant for ▼ vs ●. P < .01, ▼ and ● vs ▽. Pooled data are from 2 experiments; n = 16 mice/group total.