Phenotype of donor T cells that have reconstituted the host. [BALB/c × C57BL/6]F1 recipient mice were lethally irradiated and then grafted with 3 × 10⁶ CD3ε^−/− BM and 3 × 10⁶ allogeneic Ly5.1⁺ C57BL/6 T cells alone (Tallo) or with 3 × 10⁶ specific rsTreg (Tallo+rsTreg). The activation profile of donor Ly5.1⁺ CD4⁺ and CD8⁺ T cells was evaluated in the spleen 7, 15, 30, and 60 days after transplantation. (A) Naive (N), central memory (CM), and effector memory (EM) cells are defined as CD62L^hiCD44^low, CD62L^hiCD44^hi, and CD62L^lowCD44^hi, respectively. Representative dot plots of the activation profile of Ly5.1⁺ CD4⁺ and CD8⁺ T cells are shown 7, 15, 30, and 60 days posttransplantation. Numbers in each quadrant indicate the percentage of cells. (B) The mean percentage of naive, CM, and EM Ly5.1⁺ CD4⁺ and CD8⁺ T cells is represented at 7, 15, 30, and 60 days posttransplantation for Tallo (▵) and Tallo+rsTreg (▴). Symbols represent the mean percentage of cells and bars are the SD. At day 7, n = 5 from 1 experiment; at day 15, n = 5 to 7 from 2 independent experiments; at day 30, n = 2 to 8 from 3 independent experiments; at day 60, n = 8 from 2 independent experiments. *P < .05 for Tallo vs Tallo+rsTreg.