目的：分析支链氨基酸（BCAAs）在重症肌无力(MG)患者外周血中的变化，探讨其在实验性自身免疫 性重症肌无力（EAMG）模型中的免疫调节作用。方法：收集54例MG患者纳入MG组，另设35例健康体检 者为对照组，采用液相色谱-质谱分析检测血中BCAAs水平、淋巴细胞亚群和细胞因子，比较2组的差异。 使用BCAAs喂养EAMG小鼠，评估其肌力变化，并采用ELISA方法检测细胞因子水平。结果：与对照组相 比，MG组患者血缬氨酸、异亮氨酸水平降低，而TNF-α、IL-6、IL-8水平升高（P＜0.05）。与正常饮食组相 比，BCAAs饮食组小鼠症状较轻且TNF-α、IL-6、IL-8水平降低（P＜0.05）。结论：BCAAs有益于改善MG的 免疫反应，通过调节BCAAs的代谢或其相关的转运蛋白及信号通路有可能成为调节MG免疫的新切入点。

To analyze the change of branched chain amino acids (BCAAs) level in peripheral serum of patients with myasthenia gravis (MG), and to explore its immunomodulatory role in the experimental autoimmune myasthenia gravis (EAMG) animal model. Methods: Total 54 MG patients (MG group) and 35 healthy controls (control group) were enrolled respectively. Liquid chromatography - mass spectrometry testing was used to detect the levels of BCAAs, lymphocyte subsets, and cytokines in both groups, and the results were compared. EAMG mice were fed by BCAAs, then changes to muscle strength were evaluated and cytokine levels were detected by ELISA. Results: Compared with those of the control group, the levels of Val and Ile in the MG group were lower, and the levels of TNF-α, IL-6, IL-8 were higher (P<0.05). Compared with normal diet EAMG mice, the BCAA-fed mice showed significantly reduced clinical scores and levels of TNF-α, IL-6, and IL-8 (P<0.05). Conclusion: BCAAs are helpful in improving immune response in MG. Through adjustments to BCAAs metabolism or their transport proteins, a new route for regulating immunity in MG may be established.