Department of Neuropaediatrics, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Department of Neurology, Charité - Universitätsmedizin Berlin and German Center for Neurodegenerative Diseases (DZNE) Berlin, Berlin, Germany.
Brain Res. 2019 Feb 1;1704:249-256. doi: 10.1016/j.brainres.2018.10.019. Epub 2018 Oct 19.
The y-aminobutyric acid A receptor (GABAR) participates in most neurophysiological processes. Mutations cause epilepsy and neuropsychiatric pathologies. Recently a severe encephalitis with refractory seizures and antibodies against GABARs has been described. Considering the complex subunit distribution of GABARs, binding patterns of human GABAR antibodies will help to understand the pathophysiology underlying diverse clinical pictures. We therefore investigated the cerebrospinal fluid (CSF) reactivity of a patient with GABAR encephalitis using immunocytochemistry on murine brain sections and compared its specificity with commercial GABAR antibodies. The immunoreactivity of the patient's CSF showed excellent agreement with previously reported GABAR mRNA expression. Colocalization with neuronal and glial markers verified the neuronal specificity of GABAR. Patient antibodies strongly bound to neuropil in the external layers of the olfactory bulb, CA1 and CA2 of the hippocampus, neocortex, pallidum and granular cells of the cerebellum. Distribution patterns suggest the presence of polyclonal CSF GABAR antibodies targeting multiple receptor subunits. The comparison with commercial antibodies revealed large overlap, but also specific differences. For example, commercial antibodies accumulated on dendrites, while CSF created a homogeneous neuropil signal. The number of GABAergic synapses stained with CSF exceeded those labeled with the commercial antibodies. In some areas, commercial antibodies and CSF even stained complementary populations of GABAergic neurons. The data indicate the presence of additional anti-neuronal autoantibodies in the CSF, which could be assessed in future studies with individual recombinant monoclonal antibodies from CSF B cells. This strategy would confirm antibody pathogenicity and likely explain variable clinical pictures in autoimmune encephalitis patients.
γ-氨基丁酸 A 受体（GABAR）参与大多数神经生理过程。突变会导致癫痫和神经精神病理学。最近，描述了一种严重的脑炎，伴有难治性癫痫发作和针对 GABAR 的抗体。考虑到 GABAR 的复杂亚基分布，人 GABAR 抗体的结合模式将有助于理解不同临床特征背后的病理生理学。因此，我们使用鼠脑切片免疫细胞化学研究了 GABAR 脑炎患者脑脊液（CSF）的反应性，并将其特异性与商业 GABAR 抗体进行了比较。患者 CSF 的免疫反应性与先前报道的 GABAR mRNA 表达高度一致。与神经元和神经胶质标志物的共定位验证了 GABAR 的神经元特异性。患者抗体强烈结合嗅球外皮层、海马 CA1 和 CA2、新皮层、苍白球和小脑颗粒细胞的神经胶质。分布模式表明存在针对多个受体亚基的多克隆 CSF GABAR 抗体。与商业抗体的比较显示出很大的重叠，但也有特异性差异。例如，商业抗体在树突上积累，而 CSF 则产生均匀的神经胶质信号。用 CSF 染色的 GABA 能突触数量超过用商业抗体标记的数量。在某些区域，商业抗体和 CSF 甚至标记了互补的 GABA 能神经元群体。这些数据表明 CSF 中存在额外的抗神经元自身抗体，未来可以使用 CSF B 细胞的个体重组单克隆抗体进行评估。这种策略将证实抗体的致病性，并可能解释自身免疫性脑炎患者的可变临床特征。
