Heterogeneity of meningeal B cells reveals a lymphopoietic niche at the CNS borders [scRNA-seq]. Heterogeneity of meningeal B cells reveals a lymphopoietic niche at the CNS borders [scRNA-seq]

The meninges contain adaptive immune cells that provide immunosurveillance of the CNS. These cells are thought to derive from the systemic circulation. Through single cell analyses, confocal 35 imaging, bone marrow chimeras and parabiosis experiments, we show that meningeal B cells derive locally from the calvaria, which harbors a bone marrow niche for hematopoiesis. B cells reach the meninges from the calvaria through specialized vascular connections. This calvaria- meningeal path of B cell development may provide the CNS with a constant supply of B cells educated by CNS antigens. Conversely, we show that a subset of antigen-experienced B cells that 40 populate the meninges in aging mice are blood-borne. These results identify a private source for meningeal B cells which may help maintain immune privilege within the CNS. Overall design: scRNA-seq was performed on bulk preparations from mouse peripheral blood, tibial bone marrow, and dura mater from young and aged mice. Sequencing was completed in two batches: The first batch contained 3 mice from each age:tissue combination. The second batch contained peripheral blood and dura from 3 young and 4 old mice.

脑膜（meninges）中存在适应性免疫细胞，负责执行中枢神经系统（CNS）的免疫监视。这类细胞被认为源自体循环。通过单细胞分析、共聚焦成像、骨髓嵌合体实验以及联体共生实验，我们证实脑膜B细胞局部起源于颅骨（calvaria）——颅骨内存在造血相关的骨髓微环境。B细胞通过特化的血管连接从颅骨迁移至脑膜。这种颅骨-脑膜的B细胞发育路径，可为中枢神经系统持续提供经中枢神经系统抗原致敏的B细胞。与之相反，我们发现衰老小鼠脑膜中存在的一类抗原致敏B细胞亚群则源自血液循环。本研究结果明确了脑膜B细胞的专属来源，该来源或有助于维持中枢神经系统内的免疫特权。整体实验设计：对幼年与衰老小鼠的外周血、胫骨骨髓以及硬脑膜的批量样本进行了单细胞RNA测序（scRNA-seq）。测序分为两个批次完成：第一批次包含每一种年龄-组织组合对应的3只小鼠样本；第二批次则包含3只幼年小鼠与4只衰老小鼠的外周血及硬脑膜样本。