CD44^hi T cells are donor BM-derived and persistently apoptotic in recipients of MHC-mismatched or MHC-matched allogeneic TCD-BMT or syngeneic TCD-BMT. (A) Lethally irradiated (850 cGy) 8- to 10-week-old BALB/c mice were transplanted with 10⁵ lineage-depleted RAG2-eGFP Tg BM and harvested on day 42. Donor-derived (H-2D^d negative) CD4⁺ and CD8⁺ T cells were analyzed. Data representative of 2 independent experiments is shown. (B) Lethally irradiated (850 cGy) 8- to 10-week-old BALB/c mice were transplanted with 10⁵ lineage-depleted B6 BM and harvested at day 42. Donor-derived (H-2D^d negative) CD4⁺ and CD8⁺ splenic T cells were analyzed for apoptosis with annexin-V staining. (C) Mice received transplants and were harvested as in (B), and the intracellular levels of Bcl-2 in donor CD44^hi and CD44^lo, CD4⁺ and CD8⁺ T-cell subsets were determined. (D) Lethally irradiated (850 cGy) 8- to 10-week-old B6 mice were transplanted with 10⁵ lineage-depleted B6 Ly5.1⁺ BM and harvested at day 42. Percentages of apoptotic donor-derived (H-2D^d negative) T cells were determined by annexin-V staining. n = 5. (E) Lethally irradiated (850 cGy) 8- to 10-week-old BALB/c mice were transplanted with 10⁴ purified B6 LSK stem cells and analyzed on day 52. Percentages of apoptotic donor-derived (H-2D^d negative) T cells were determined by annexin-V staining (n = 5).