Sirt-1 regulates T-cell proliferation, differentiation, and aGVHD pathogenicity. (A) Purified T cells from either WT or Sirt-1^−/− donors (H-2^b) were labeled with CFSE and transferred into lethally irradiated BALB/c (H-2^d) mice at 2 × 10⁶ cells per mouse. Three days after cells transfer, recipient spleens were harvested and analyzed by flow cytometry. Representative figures and percentages of CFSE and IFN-γ are shown on gated live cells followed by H-2^b+CD4⁺ or CD8⁺ cells. (B) Average percentages of CFSE-diluted and IFN-γ⁺ cells are shown on gated live donor CD4⁺ or CD8⁺ T cells in recipient spleen (n = 5 mice/group). (C-E) Lethally irradiated BALB/c (700 cGy) mice underwent transplantation with 5 × 10⁶ TCD-BM per mouse plus 0.7 × 10⁶ CD25-depleted T cells. (C) Survival, (D) bodyweight loss, and (E) clinical scores were monitored. (F-G) Tissues from BALB/c recipients were collected on day 14 after allo-BMT and analyzed for pathology. (G) Hematoxylin and eosin staining of representative pictures of livers and large intestines are shown (n = 10 mice/group). Original magnification ×200. Log-rank (Mantel-Cox) test was used to analyze the survival curve. Student t test was used for statistical analysis. *P < .05; **P < .01; ***P < .001; ****P < .0001.