High TOX expression on CD8 + T cells in pure red cell aplasia

Thymocyte selection-associated high-mobility group box protein (TOX) is an important molecule regulating the development and exhaustion of T lymphocytes. Our aim is to investigate the role of TOX in the immune pathogenesis of pure red cell aplasia (PRCA). TOX expression of CD8 + lymphocytes from the peripheral blood of patients with PRCA was detected by flow cytometry. Additionally, the expression of immune checkpoint molecules PD1 and LAG3 and cytotoxic molecules perforin and granzyme B of CD8 + lymphocytes was measured. The quantity of CD4 + CD25 + CD127 low T cells was analyzed. TOX expression on CD8 + T lymphocytes in PRCA patients was significantly increased (40.73 ± 16.03 vs. 28.38 ± 12.20). The expression levels of PD1 and LAG3 on CD8 + T lymphocytes in PCRA patients were significantly higher than those in the control group (34.18 ± 13.26 vs. 21.76 ± 9.22 and 14.17 ± 13.74 vs. 7.24 ± 5.44, respectively). The levels of perforin and granzyme in CD8 + T lymphocytes of PRCA patients were 48.60 ± 19.02 and 46.66 ± 25.49, respectively, which were significantly higher than those of the control group (31.46 ± 7.82 and 16.17 ± 4.84, respectively). The number of CD4 + CD25 + CD127 low Treg cells in PRCA patients was significantly decreased (4.30 ± 1.27 vs. 1.75 ± 1.22). In PRCA patients, CD8 + T cells were activated and exhibited overexpression of TOX, PD1, LAG3, perforin, and granzyme B, while regulatory T cells decreased. These findings suggest that T cell abnormality plays a critical role in the pathogenesis of PRCA.