[Effects of donor T cell stat3 deficiency on acute intestinal graft-versus-host disease in mice].

<b>Objective:</b> To investigate the effects and underlying mechanisms of Stat3 knockout in donor T cells on acute gastrointestinal graft-versus-host disease (GI-aGVHD) . <b>Methods:</b> BALB/c mice were exposed to lethal irradiation and transplanted with bone marrow and spleen cells from BALB/c mice (syngeneic control group), C57BL/6 mice (wild-type T cell group, WT group), or C57BL/6J-Stat3(em1cyagen) mice (Stat3 gene knockout T cell group, Stat3-KO group) via tail vein injection to establish the aGVHD model. The survival rate, body weight changes, and clinical scores of mice were monitored. Cytometric bead array (CBA) was used to detect the concentrations of serum cytokines. Lymphocytes were isolated from tissues for flow cytometric analysis. H&E staining was performed to observe intestinal pathological changes. FITC-dextran assay was conducted to assess intestinal permeability. Immunohistochemistry was used to evaluate the expression of Ki67 and Muc2. Real-Time Quantitative Reverse Transcription PCR (qRT-PCR) was employed to analyze the gene expression levels of Olfm4, Lysozyme, and Muc2 in the small intestine. Metabolomics was conducted to detect metabolites in serum and intestinal tissues. An in vitro GI-aGVHD organoid model was established by coculturing intestinal organoids with allogeneic T cells, where the number and area of small intestinal organoids were recorded. The GVL effect was assessed using luciferase-transfected ALL cells (ALL/Luc) and bioluminescent imaging. <b>Results:</b> Compared with the WT group, Stat3 knockout T cells alleviated body weight loss, reduced symptoms-such as hunchback and diarrhea-in mice, improved survival rate (<i>P</i><0.05), and reduced serum interleukin (IL) -2, IL-6, interferon-γ, tumor necrosis factor-α, IL-17A, and IL-10 levels (all <i>P</i><0.05), intestinal inflammatory cell infiltration (<i>P</i><0.05), and intestinal mucosal permeability. Further, Muc2 and Ki67 expression levels in the small intestine of the Stat3 knockout group were markedly increased, and Olfm4, Lysozyme, and Muc2 gene expression levels were significantly increased (all <i>P</i><0.05). In vitro, the Stat3 knockout group demonstrated better organoid development than the WT group. Metabolomic analyses indicated that Stat3 knockout in T cells may affect the pathways associated with bile acid secretion and unsaturated fatty acids. ALL/Luc cells in the GVL mouse model proliferated rapidly in the TCD-BM group; however, 80% of the mice in the Stat3-KO group survived tumor-free for >100 days (<i>P</i><0.05) . <b>Conclusion:</b> Knocking out Stat3 in graft T cells reduces T cell damage to intestinal stem cells, thereby ultimately alleviating GI-aGVHD while maintaining a stable GVL effect.