ELISAs
Plasma samples from 78 of 103 patients with MG were selected (no statistically significant differences in sex, age, MGFA classification and thymic histology of patients from whom specimens were selected were observed compared with the general population), and plasma from 30 of 36 healthy volunteers was. Detailed information regarding the samples is presented in Supplementary Table 1 . Meanwhile, plasma samples from 37 patients with USMG, 34 patients with RSMG and 30 patients with PSMG were selected from the plasma sample bank of the First Affiliated Hospital of Soochow University from July 2017 to May 2021, and the clinical characteristics of patients with different stages of MG are shown in Supplementary Table 3 . In addition, plasma sOX40 and sOX40L expression levels were detected in 13 patients with MG in the recurrence and remission stages. The frozen plasma specimens were thawed at room temperature and centrifuged at 2000 rpm for 5 minutes, and the plasma supernatant was taken for enzyme-linked immunosorbent assay (ELISA). The concentrations of AchR-Ab were detected in plasma samples from all patients with MG using the Human Acetylcholine Receptor Autoantibody ELISA Kit (RSR Biotechnology Co., Ltd., UK). Plasma levels of sOX40 and sOX40L were measured using ELISAs (human sOX40 and sOX40L reagent kits were obtained from Shanghai Kang Lang Biological Technology Co., Ltd., Shanghai, China). The specific experimental procedures used for ELISAs were performed according to the manufacturer’s instructions.