MuSK myasthenia gravis monoclonal antibodies
MuSK myasthenia gravis monoclonal antibodies
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DOI：
10.1212/nxi.0000000000000547
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发表时间：
2019-05-01
影响因子：
8.8
通讯作者：
Verschuuren, Jan J.
中科院分区：
文献类型：
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作者：
Huijbers, Maartje G.;Vergoossen, Dana L.;Verschuuren, Jan J.
目的从麝香型重症肌无力（MG）患者中分离肌肉特异性激酶（MuSK）单克隆抗体，并从遗传和功能水平上对其进行鉴定。方法从患者源性麝香特异性克隆B细胞中制备重组麝香抗体，并制备单价Fab片段。在肌管培养中，检测了抗体和Fab片段对神经agrin诱导的MuSK磷酸化和乙酰胆碱受体（AChR）聚集的影响。结果分离到的麝香单克隆抗体序列包括IgG1、IgG3和IgG4，它们经历了高水平的亲和成熟，符合抗原选择。我们证实了它们对MuSK Ig-like 1结构域的特异性以及与神经肌肉连接的结合。单价麝香Fab，模拟功能性单价麝香MG患者的Fab臂交换血清IgG4，消除了agrin诱导的麝香磷酸化和AChR聚集。令人惊讶的是，二价单特异性麝香抗体反而激活了麝香磷酸化并部分诱导AChR聚集，不依赖于agrin。结论根据麝香结合位点的数量不同，患者源性麝香抗体可作为麝香激动剂或麝香拮抗剂。患者血清中Fabarm交换诱导的功能性单价使MuSK IgG4抗体具有致病性。
ObjectiveTo isolate and characterize muscle-specific kinase (MuSK) monoclonal antibodies from patients with MuSK myasthenia gravis (MG) on a genetic and functional level.MethodsWe generated recombinant MuSK antibodies from patient-derived clonal MuSK-specific B cells and produced monovalent Fab fragments from them. Both the antibodies and Fab fragments were tested for their effects on neural agrin-induced MuSK phosphorylation and acetylcholine receptor (AChR) clustering in myotube cultures.ResultsThe isolated MuSK monoclonal antibody sequences included IgG1, IgG3, and IgG4 that had undergone high levels of affinity maturation, consistent with antigenic selection. We confirmed their specificity for the MuSK Ig-like 1 domain and binding to neuromuscular junctions. Monovalent MuSK Fab, mimicking functionally monovalent MuSK MG patient Fab-arm exchanged serum IgG4, abolished agrin-induced MuSK phosphorylation and AChR clustering. Surprisingly, bivalent monospecific MuSK antibodies instead activated MuSK phosphorylation and partially induced AChR clustering, independent of agrin.ConclusionsPatient-derived MuSK antibodies can act either as MuSK agonist or MuSK antagonist, depending on the number of MuSK binding sites. Functional monovalency, induced by Fabarm exchange in patient serum, makes MuSK IgG4 antibodies pathogenic.