Table 1_Subtype-specific atypical B cell profiles in myasthenia gravis reveal distinct immunopathological pathways.docx

IntroductionAtypical B cell (atBC) subsets display significant heterogeneity across autoimmune diseases, complicating efforts to define their role and therapeutic potential. We hypothesized that this heterogeneity reflects the responses to specific immunopathology, resulting in disease-specific profiles. The myasthenia gravis (MG) subtypes acetylcholine receptor (AChR)-positive MG and muscle-specific kinase (MuSK)-positive MG provide an ideal model to explore atBCs due to the distinct immune mechanisms driven by IgG1-3 and IgG4 autoantibodies, respectively in the disease.
MethodsCD11c+ and IgD−CD27− double-negative (DN) B cells were analyzed by spectral flow cytometry in non-autoimmune controls, AChR-MG, and MuSK-MG. Results were correlated with clinical parameters and antibody levels. In MG subtypes, atBC subsets were further examined for the impact of disease onset and prior rituximab treatment. CD11c+ B cells were stimulated in vitro to assess antibody secreting cell (ASC) differentiation.
ResultsCD11c+ and DN2 B cells were increased in late-onset AChR-MG, while MuSK-MG featured expanded DN3 B cells linked to disease severity. CD20 expression in atBCs was differentially expressed between MG subtypes, with higher levels in late-onset AChR-MG and significantly reduced levels in MuSK-MG. CD11c+ B cells were reduced after anti-CD20 treatment in MuSK-MG, whereas DN B cells were unaffected. Functionally, CD11c+ B cells from MuSK-MG exhibited greater ASC differentiation and autoantibody production.
DiscussionMG subtypes exhibit distinct atBC profiles linked to immunopathology and disease onset. These findings reveal subtype-specific pathways that regulate atBCs and highlight their potential as therapeutic targets in both IgG1-3- and IgG4-mediated autoimmunity.

引言：非典型B细胞（atypical B cell, atBC）亚群在各类自身免疫病中呈现显著异质性，这为明确其功能角色与治疗潜力带来了极大挑战。我们推测，这种异质性源于对特定免疫病理过程的应答，进而形成疾病特异性的细胞特征图谱。由于重症肌无力（myasthenia gravis, MG）的两个亚型——乙酰胆碱受体阳性重症肌无力（acetylcholine receptor (AChR)-positive MG）与肌肉特异性激酶阳性重症肌无力（muscle-specific kinase (MuSK)-positive MG）——分别由IgG1-3与IgG4自身抗体介导独特的免疫发病机制，二者成为探索atBC的理想模型。方法：我们通过光谱流式细胞术，对非自身免疫对照人群、AChR-MG患者及MuSK-MG患者的CD11c⁺与IgD⁻CD27⁻双阴性（double-negative, DN）B细胞进行分析，并将检测结果与临床参数及抗体水平进行关联。在MG亚型中，我们进一步探究了疾病起病时机与既往利妥昔单抗治疗对atBC亚群的影响。此外，我们体外刺激CD11c⁺ B细胞，以评估其抗体分泌细胞（antibody secreting cell, ASC）分化潜能。结果：迟发性AChR-MG患者体内CD11c⁺ B细胞与DN2 B细胞水平升高；而MuSK-MG患者则表现出与疾病严重程度相关的DN3 B细胞扩增。atBC表面CD20的表达在MG亚型间存在差异：迟发性AChR-MG患者的atBC CD20表达水平更高，而MuSK-MG患者的atBC CD20水平则显著降低。MuSK-MG患者经抗CD20治疗后，CD11c⁺ B细胞数量减少，但DN B细胞未受影响。功能实验显示，MuSK-MG患者来源的CD11c⁺ B细胞具有更强的ASC分化能力与自身抗体产生能力。讨论：MG不同亚型具有各自独特的atBC细胞特征图谱，且与免疫病理及疾病起病时机相关。本研究结果揭示了调控atBC的亚型特异性通路，同时凸显了atBC作为IgG1-3与IgG4介导的自身免疫性疾病治疗靶点的潜在价值。