Cd8(+)Gitr(+)T Cells May Negatively Regulate T Cell Overactivation In Aplastic Anemia

Aplastic anemia (AA) is a T cell immune-mediated autoimmune disease. Overactivated CD8(+)T cells play a leading role in the pathogenesis of AA, which may be due to disbalance in costimulatory and coinhibitory signals in T cells. In this study, we firstly investigated the expression of OX40, 4-1BB, GITR, ICOS, CTLA-4, LAG-3, and TIM-3 on CD8(+)T cells from untreated patients with AA and healthy individuals (HIs) by flow cytometry. Moreover, we further analyzed the phenotype and functional characteristics of CD8(+)GITR(+)T cells to more fully assess the T cell activation dysfunction in AA. We for the first time demonstrated significantly decreased percentage of CD8(+)GITR(+)T cells in AA, and CD8(+)GITR(+)CTLA-4(+)T cells were significantly higher in patients with AA compared with HIs. Conversely, the percentage of CD8(+)GITR(+)granzyme B(+)and CD8(+)GITR(+)perforin(+)T cells in AA patients was significantly reduced. Our preliminary data illustrate that the CD8(+)GITR(+)T cell population might negatively regulate overactive T cell activation in AA.