Origin and diversity of pathogenic human monoclonal antibodies to the NMDA receptor

在抗NMDA受体（NMDAR）脑炎中，针对NMDAR的GluN1亚基的自身抗体引起独特的神经精神综合征。我们最近从NMDAR脑炎患者的脑脊液浆细胞中克隆了第一个人单克隆GluN1自身抗体。抗体诱导的突触病理学类似于患者来源的IgG。到目前为止，还不清楚体液自身免疫反应是如何触发的，抗体产生细胞是否在外周发育并迁移到大脑中，以及个体自身抗体的致病潜力是否取决于亲和力成熟的程度或其生物物理特性。在这里，我们将通过抗体克隆和表达，在单细胞水平上对血清和脑脊液来源的B细胞进行功能比较，研究NMDAR脑炎中抗体产生细胞的起源。具体来说，我们将研究单克隆抗体是否与原代神经元、人诱导多能干细胞（iPSC）和脑切片中的突触靶点反应。此外，我们将确定它们的亲和力和它们在小鼠模型中被动转移后的致病作用。我们将进一步评估导致继发性自身免疫性脑炎的病毒感染或肿瘤是否包含抗NMDAR抗体库。使用我们建立的单细胞克隆技术，我们还旨在从自身免疫性脑炎的其他亚型中鉴定致病抗体，例如具有抗GABAB受体抗体和抗LGI1自身抗体的脑炎。

In anti-NMDA receptor (NMDAR) encephalitis, autoantibodies against the GluN1 subunit of the NMDAR cause a distinct neuropsychiatric syndrome. We recently cloned the first human monoclonal GluN1 autoantibodies from cerebrospinal fluid plasma cells of NMDAR encephalitis patients. The antibodies induced synaptic pathology similar to patient-derived IgG. So far, it is unclear how the humoral autoimmune response is triggered, whether antibody-producing cells develop in the periphery and migrate into the brain, and whether individual autoantibodies differ in their pathogenic potential depending on the degree of affinity maturation or their biophysical properties. Here, we will investigate the origin of antibody-producing cells in NMDAR encephalitis by functional comparison of serum and cerebrospinal fluid-derived B cells at single-cell level through antibody cloning and expression. Specifically, we will investigate if the monoclonal antibodies react with synaptic targets in primary neurons, in human induced pluripotent stem cells (iPSC), and in brain sections. Furthermore, we will determine their affinity and their pathogenic effect upon passive-transfer in mouse models. We will further assess whether viral infections or tumors leading to secondary autoimmune encephalitis encompass anti-NMDAR antibody repertoires. Using our established single-cell cloning techniques, we also aim to identify disease-causing antibodies from other subtypes of autoimmune encephalitis, such as encephalitis with anti-GABAB receptor antibodies and with anti-LGI1 autoantibodies.