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Abstract：
Intrathecal synthesis of central nervous system (CNS)-reactive autoantibodies is observed across patients with autoimmune encephalitis (AE), who show multiple residual neurobehavioral deficits and relapses despite immunotherapies. We leveraged two common forms of AE, mediated by leucine-rich glioma inactivated-1 (LGI1) and contactin-associated protein-like 2 (CASPR2) antibodies, as human models to comprehensively reconstruct and profile cerebrospinal fluid (CSF) B cell receptor (BCR) characteristics. We hypothesized that the resultant observations would both inform the observed therapeutic gap and determine the contribution of intrathecal maturation to pathogenic B cell lineages. From the CSF of three patients, 381 cognate-paired IgG BCRs were isolated by cell sorting and scRNA-seq, and 166 expressed as monoclonal antibodies (mAbs). Sixty-two percent of mAbs from singleton BCRs reacted with either LGI1 or CASPR2 and, strikingly, this rose to 100% of cells in clonal groups with ≥4 members. These autoantigen-reactivities were more concentrated within antibody-secreting cells (ASCs) versus B cells (P < 0.0001), and both these cell types were more differentiated than LGI1- and CASPR2-unreactive counterparts. Despite greater differentiation, autoantigen-reactive cells had acquired few mutations intrathecally and showed minimal variation in autoantigen affinities within clonal expansions. Also, limited CSF T cell receptor clonality was observed. In contrast, a comparison of germline-encoded BCRs versus the founder intrathecal clone revealed marked gains in both affinity and mutational distances (P = 0.004 and P < 0.0001, respectively). Taken together, in patients with LGI1 and CASPR2 antibody encephalitis, our results identify CSF as a compartment with a remarkably high frequency of clonally expanded autoantigen-reactive ASCs whose BCR maturity appears dominantly acquired outside the CNS.
摘要：
在自身免疫性脑炎（AE）患者中观察到中枢神经系统（CNS）反应性自身抗体的鞘内合成，尽管进行了免疫疗法，但仍表现出多种残留的神经行为缺陷和复发。我们利用了两种常见的AE形式，由富含亮氨酸的神经胶质瘤灭活-1（LGI1）和接触蛋白相关蛋白样2（CASPR2）抗体介导，作为人类模型来全面重建和描绘脑脊液（CSF）B细胞受体（BCR）特征。我们假设所得的观察结果将告知观察到的治疗差距，并确定鞘内成熟对致病性B细胞谱系的贡献。从三个病人的脑脊液中，通过细胞分选和scRNA-seq分离381个同源配对的IgGBCR，和166表达为单克隆抗体(mAb)。来自单例BCR的mAb中有62％与LGI1或CASPR2反应，惊人的,在具有≥4个成员的克隆组中,这一比例上升到100%.与B细胞相比，这些自身抗原反应性更集中在抗体分泌细胞（ASC）内（P<0.0001），并且这两种细胞类型都比LGI1-和CASPR2-不反应的对应物更分化。尽管差异更大，自身抗原反应性细胞在鞘内获得的突变很少，并且在克隆扩增中的自身抗原亲和力变化最小。此外，观察到有限的CSFT细胞受体克隆性。相比之下,种系编码的BCRs与建立者鞘内克隆的比较显示，亲和力和突变距离均显着增加（分别为P=0.004和P<0.0001）。一起来看,在LGI1和CASPR2抗体脑炎患者中，我们的结果将CSF确定为具有非常高频率的克隆扩增的自身抗原反应性ASC的区室,其BCR成熟度似乎主要在CNS外部获得.
