Activation and exhaustion markers were increased on kidney-infiltrating donor T cells from allogeneic recipients. BALB/c (H-2^d) animals were lethally irradiated and received transplantation with CD90.2⁺ splenic T cells together with BM cells from either syn BALB/c or allo MHC-mismatched B6 (H-2^b) donors. On day 14 after HCT, T cells infiltrating the kidneys (H-2Kd⁺ cells in syn recipients or H-2Kb⁺ cells in allo recipients) were analyzed by flow cytometry. (A) Representative dot plots of donor T-cell (CD3⁺) expansion in the kidneys are shown. (B) Absolute numbers of total CD3⁺CD4⁺ and CD3⁺CD8⁺ cells among gated live donor cells infiltrating the kidneys are shown. (C-D) Subsets of donor-derived CD4⁺ T cells (top) and CD8⁺ T cells (bottom) in the kidney of the allo-HCT recipients are shown. Representative dot plots (C) and percentages of each subset (D) are shown. (E-H) T-cell activation (CD69 and CD25) and exhaustion (PD-1 and Tim-3) markers were analyzed in CD3⁺CD4⁺ and CD3⁺CD8⁺ populations. CD69 (E), CD25 (F), PD-1 (G), and Tim-3 (H) were higher in the allo group; n = 3 to 5 mice per group. Data representing 3 experiments are shown. The bars depict the mean ± SEM. Student t test was used for statistical analysis for panels B,E-H. Naïve, naïve T cell (CD44⁻CD62L⁺); CM, central memory T cell (CD44⁺CD62L⁺); EM, effector memory T cell (CD44⁺CD62L⁻).