Signifcance of Intestinal CD8+CD69+CD103+ Tissue-Resident Memory T Cells in Human Intestinal Acute Graft-Versus-Host Disease

Background: Gastrointestinal acute graft-versus-host disease (aGVHD) is a serious complication and a leading cause of mortality following allogeneic hematopoietic stem cell transplantation (allo-HSCT). Recently, tissue-resident memory T cells (TRM) cells in tissue-specific immune and inflammatory diseases is beginning to be appreciated. However, CD8+TRM cells have not been fully elucidated regarding their changes and functions in human intestinal aGVHD. In this study, we used CD69 and CD103 as surrogate markers of human CD8+TRM cells.We performed functional analyses of CD8+TRM cells to explore the role of these cells in the development of human intestinal aGVHD. Method： 51 intestinal aGVHD patients after allo-HSCT and 31 healthy controls were enrolled in this study. Clinical symptoms of the patients were evaluated according to the MAGIC criteria. Among 51 intestinal aGVHD patients, 13 patients have mild aGVHD and 38 have severe aGVHD. Colonoscopy was performed to obtain biopsy samples from diseased and healthy tissues. Histopathological scoring of intestinal aGVHD was conducted using HE staining, and the number and function of CD8+CD69+CD103+ TRM cells in the intestine were detected by immunofluorescence and flow cytometry. Results: In this study,the pathological scores of patients correlated with clinical grading (Figure A). We use CD69 and CD103 as surrogate markers of human CD8+TRM cells,CD8+CD69+CD103+ TRM cells were clearly present in the intestines of patients post-allo-HSCT. These CD8+TRM cells did not express CCR7 or CD62L and exhibited tissue-resident characteristics(Figure B-C). Compared to healthy controls, the absolute number of CD8+ T cells in the intestinal tissues of aGVHD patients was significantly increased(Figure D), while the absolute number and proportion of CD8+CD69+CD103+ TRM cells were significantly decreased (P<0.0001)(Figure E),. Furthermore, patients with severe aGVHD showed a further reduction in CD8+CD69+CD103+ TRM cells compared to those with mild aGVHD, correlating with the clinical symptom grading(R=0.6181,P<0.0001) (Figure F-G) . The association of CD8+TRM cells with a progressive clinical course of human Intestinal acute Graft-versus-Host Disease are independent of patient age, days post-transplantation, primary disease, transplantation method, graft source, GVHD prophylaxis,or myeloablative conditioning regimen.We further demonstrated that there was similar expression of cytotoxic protein(Granzyme B and Perforin) in CD8+CD69+CD103+ TRM cells between severe aGVHD and mild aGVHD patients, while the expression of inhibitory receptors (PD1 and CTLA4) was significantly increased in severe aGVHD patients (P<0.01) (Figure H). Conclusion: In conclusion, the CD8+CD69+CD103+ TRM cell subset is significantly reduced in intestinal aGVHD patients and correlates with disease severity.CD8+CD69+CD103+ TRM cells have higher expression of immunoregulatory molecules in severe aGVHD patients.Our results suggest that the frequency of CD8+CD69+CD103+ TRM cells is associated with the clinical course of human intestinal aGVHD and potentially hinder its development.Our study will provide new insights for the diagnosis and treatment of human intestinal aGVHD.