Origin, fate, and function of meningeal mature and progenitor B cells.

中枢神经系统（CNS）由脑脊液（CSF）和称为脑膜的纤维膜包裹。两者都具有免疫相关的功能，但这些CNS相关的边界区室中淋巴细胞的组成和功能尚不清楚。在我们之前的结果中，我们进行了三个关键的观察：1）每个CNS相关的边界隔室隔室中的淋巴细胞组成是独特的，2）即使是稳态硬脑膜，但没有其他隔室，也含有丰富的B细胞，3）令人惊讶的是，健康啮齿动物硬脑膜也含有处于前B细胞阶段的B细胞祖细胞。在进一步的后续实验中，我们证实了硬脑膜在实验性神经炎症中宿主B细胞的倾向。我们还观察到转录因子Bcl 6通过促进B细胞主导的脑膜炎症在Th17细胞中发挥非典型功能。因此，我们确定了控制脑膜与实质炎症区室化的关键机制。基于这些以前的观察，我们在这里计划了解脑膜和颅骨BM驻留B细胞和B细胞祖细胞的起源，命运和功能。在这方面的关键技术挑战是实现白细胞的位置特异性标记和调节。在本提案的这一挑战的准备，我们已经建立了跨颅骨骨和颅骨内标记与示踪染料和光转换的脑膜和颅骨骨髓B细胞表达的光转换荧光蛋白。我们还获得了以位点特异性方式消耗B细胞的资源。有了这个实验“工具包”，我们现在的目标是解决脑膜B细胞和B细胞祖细胞是否直接来源于颅骨骨髓或次级淋巴器官，以及它们从脑膜的交通。然后，我们将通过经颅骨途径应用小分子抑制剂并将抗CD20 B细胞耗竭抗体注射到小脑延髓池中，来测试脑膜B细胞在神经炎症中的功能相关性。最后，我们的目标是确定新的机制，控制脑膜驻留的B细胞在深转录表征。我们将使用体外“翻转头骨”培养系统和潜在的体内使用位点特异性抑制方法来验证新的候选物。因此，我们将研究脑膜成熟和祖B细胞的起源、命运和功能。

The central nervous system (CNS) is ensheathed by the cerebrospinal fluid (CSF) and fibrous membranes termed meninges. Both serve immune-related functions, but the composition and function of lymphocytes residing in these CNS-associated border compartments is poorly defined. In own previous results, we made three key observations: 1) the lymphocyte composition in each CNS-associated border compartment compartment is unique, 2) even the homeostatic dura, but no other compartment, contains abundant B cells, 3) surprisingly, healthy rodent dura also contains B cell progenitors at the pro-B cell stage. In further follow-up experiments, we confirmed the propensity of the dura to host B cells in experimental neuroinflammation. We also observed that the transcription factor Bcl6 serves non-canonical functions in Th17 cells by promoting B cell-dominated meningeal inflammation. We thereby identified a key mechanism controlling the compartmentalization of meningeal vs. parenchymal inflammation. Based on these previous observations, we here plan to understand the origin, fate, and function of meningeal and skull BM-resident B cells and B cell progenitors. The key technical challenge in this context is to achieve location-specific labelling and modulation of leukocytes. In preparation for this challenge of the present proposal, we have established trans-skull bone and intra-skull labelling with tracer dyes and photoconversion of meningeal and skull bone marrow B cells expressing a photoconvertible fluorescent protein. We also acquired ressources to deplete B cells in a site-specific manner. With this experimental ‘toolkit’ we now aim to address whether meningeal B cells and B cell progenitors originate directly from the skull bone marrow or from secondary lymphoid organs and where they traffic from the meninges. We will then test the functional relevance of meningeal B cells in neuro-inflammation by applying small molecule inhibitor through the trans-skull route and injecting anti-CD20 B cell-depleting antibodies into the cisterna magna. Finally we aim to identify novel mechanisms controlling meningeal residency of B cells in a deep transcriptional characterization. We will validate novel candidates using an in vitro ‘flipped skull’ culture system and potentially in vivo using site-specific approaches for inhibition. We will thereby study the origin, fate, and function of meningeal mature and progenitor B cells.