Correlation of Tc17 cells at early stages after allogeneic hematopoietic stem cell transplantation with acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) is associated with an immune dysregulation usually mediated by T lymphocytes. Recently, IL-17-producing T cells including Th17 and Tc17 cells have been implicated in immune-related diseases. However, their roles in aGVHD remain uncertain. In the study, we analyzed IL-17-producing cell recovery and association with the occurrence of aGVHD. While Th17 cells steadily recovered, Tc17 cell numbers remained unaltered during the first 3 months after transplantation. Occurrence of aGVHD was correlated with increased level of Tc17 cells at the second months after allo-SCT. Interestingly, Tc17 cells were negatively associated with CD4⁺ CD25⁺ FOXP3⁺ regulatory T (Treg) cells, which was an important prognostic predictor in patients with aGVHD. In addition, we found that Tc17 numbers increased as the increased concentrations of TGF-β and IL-6, which are known to drive Th17 polarization. These finding supported that Tc17 subset is involved in the immunopathology of aGVHD. Blocking the abnormally increased number of Tc17 may be a reasonable therapeutic strategy for aGVHD.