Objective:To investigate the modulatory function of interleukin-7 (IL-7)/CD 127 signaling pathway on CD 8+T cells in patients with myasthenia gravis (MG). Methods:Fifty-seven treatment-naive MG patients who were hospitalized in Department of Neurology, Nanyang Central Hospital between 2017 and 2020 as well as 35 healthy controls were enrolled. Peripheral blood was collected, while plasma and peripheral blood mononuclear cells were isolated. Plasma IL-7 and soluble CD 127 (sCD 127) were measured by enzyme linked immunosorbent assay (ELISA). Membrane-bound CD 127 (mCD 127) percentage in CD 8+T cells was measured by flow cytometry. The differences of above indices between different gender, onset age, afflicting with thymoma, or different Osserman type and their correlation with Quantitative Myasthenia Gravis (QMG) score were analyzed. Purified CD 8+T cells from MG patients were stimulated with recombinant human IL-7 (5 μg/L). Changes of sCD 127 and mCD 127 level were analyzed. Levels of perforin, granzyme B, interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α) in the cultured supernatants were measured by ELISA. Immune checkpoint molecules mRNA in CD 8+T cells was semi-quantified by real-time fluorescence quantitative polymerase chain reaction. Results:Plasma IL-7 level was up-regulated in MG patients compared with controls [(293.4±74.7) pg/ml vs (233.8±70.8) pg/ml, t=3.78, P<0.001], while sCD 127 level was down-regulated in MG patients compared with controls [(102.7±13.7) pg/ml vs (131.2±20.9) pg/ml, t=7.91, P<0.001]. Peripheral CD 8+T cells percentage was up-regulated in MG patients compared with controls (35.4%±7.1% vs 30.2%±7.5%, t=3.31, P=0.001), and mCD 127+CD 8+T cell percentage was also elevated (45.5%±7.7% vs 34.7%±11.5%, t=5.44, P<0.001). There were no significant differences of above indices between different gender, onset age, afflicting with thymoma, or different Osserman type. There was no significant correlation between above indices and QMG score. There were no significant differences of sCD 127 in cultured supernatants, mCD 127+CD 8+T cell percentage, or immune checkpoint molecules mRNA expression between CD 8+T cells from MG patients with and without IL-7 stimulation. IL-7 stimulation promoted the secretion of perforin [(208.1±67.2) pg/ml vs (168.8±46.2) pg/ml, t=2.16, P=0.038], granzyme B [(941.8±273.9) pg/ml vs (782.4±137.2) pg/ml, t=2.33, P=0.025], and IFN-γ [(19.1±5.2) pg/ml vs (15.3±4.5) pg/ml, t=2.47, P=0.018] by CD 8+T cells. However, there was no remarkable difference of TNF-α production between CD 8+T cells with and without IL-7 stimulation. Conclusion:Elevated IL-7-mediated signaling pathway enhanced the secretion of cytotoxic molecules and cytokines by CD 8+T cells, leading to increased activity of CD 8+T cells in MG patients.