Bim regulates the survival of in vivo-induced CD8⁺Tregs during GVHD. Lethally irradiated Balb/c mice were transplanted with B6 Rag-1 BM (8 × 10⁶) plus 0.4 × 10⁶ CD4⁺ and 0.25 × 10⁶ CD8⁺ EGFP⁻ T cells from either Foxp3^EGFP or Bim^−/−Foxp3^EGFP mice. Cohorts of mice were euthanized on days 7, 14, and 21 posttransplantation, and cells were harvested from the spleen, liver, lung, and colon. (A) Representative contour plots depicting the percentage of donor-derived CD4⁺ and CD8⁺ Foxp3⁺ or Bim^−/−Foxp3⁺ Tregs present in the specified tissues is shown. (B) The absolute number of wild type or Bim^−/− CD4⁺ and CD8⁺ Tregs in these same tissue sites. Data are derived from 10 to 15 mice per tissue at each point. *P < .05; **P < .01; ***P < .001.