Donor T cells differentiated into terminal Tex after allo-HCT. (A-H) Lethally irradiated B6D2F1 mice received transplantation with T cells purified from B6-2C-Tg and B6-CD45.1 (WT) donors combined with TCD-BM from B6 donors. FCM of CD8⁺ T cells in the spleen (top) and liver (bottom) was performed. Contour plots and proportions (means ± SEM) of PD-1 and TIGIT expression on CD8.1⁺ 2C-Tg (A-B) and CD45.1⁺ WT (E-F) CD8⁺ T cells. Representative contour plots of TOX and TCF-1 and MFI of TOX expression (means ± SEM) in 2C-Tg CD8⁺ (C-D) and WT CD8⁺ T cells (G-H). Data from 2 experiments were combined (n = 5-6 per group) and shown with the data from naïve donor mice (day 0, n = 3 per group). (I-N) Lethally irradiated B6D2F1 mice received transplantation with BM cells and splenocytes from allogeneic B6 donors. Recipient mice were intraperitoneally injected with αPD-L1 or PBS from days 0 to 28 (I-K) or days 14 to 42 (L-N). Body weight changes (means ± standard deviation; panels I,L), clinical GVHD scores (means ± standard deviation; panels J,M), and survival curves (K,N). Data from 1 of the 2 experiments are shown (n = 5 per group). ∗ P < .05; ∗∗P < .01; ∗∗∗P < .005. MFI, mean fluorescence intensity; PBS, phosphate-buffered saline.