Production of cytotoxic proteins and cytokines was increased in kidney-infiltrating donor T cells of allo-HCT 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, kidneys were harvested, and disrupted, and incubated for 5 hours with phorbol 12-myristate 13-acetate, ionomycin, brefeldin A, and monensin, followed by intracellular staining. (A-B) Donor TNF-α– (A) and IFN-γ–producing (B) T cells in the kidney at day 14 after allo-HCT are shown. (C-E) Donor granzyme B– (C-D) and perforin–producing (E) CD8⁺ T cells in the kidney on day 14 after allo-HCT are shown. Representative flow cytometry images of granzyme B (C) are shown. Blue histograms indicate isotype control. Production of granzyme B (D) and perforin (E) by renal-infiltrating cytotoxic T cells was significantly increased in allogeneic recipients; n = 3 to 5 mice per group. Data are representative of 3 experiments. The bars show the mean ± SEM. Student t test was used for statistical analysis; ∗P < .05; ∗∗P < .01; ∗∗∗P < .001.