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。两者都具有与免疫相关的功能，但驻留在这些中枢神经系统相关交界区的淋巴细胞的组成和功能尚不清楚。在我们以前的研究结果中，我们做了三个关键的观察：1)每个CNS相关的边缘室的淋巴细胞组成是独特的；2)即使是动态平衡的硬脑膜，但没有其他的室，含有丰富的B细胞；3)令人惊讶的是，健康的啮齿动物硬脑膜也含有前B细胞期的B细胞前体细胞。在进一步的后续实验中，我们证实了在实验性神经炎症中硬脑膜有寄主B细胞的倾向。我们还观察到，转录因子Bcl6通过促进以B细胞为主的脑膜炎症，在Th17细胞中发挥非规范功能。因此，我们确定了控制脑膜和实质炎症分区化的关键机制。基于这些先前的观察，我们计划在这里了解脑膜和颅骨BM驻留的B细胞和B细胞前体细胞的起源、命运和功能。在这方面的关键技术挑战是实现对白细胞的特定位置标记和调节。为了应对本提案的这一挑战，我们建立了示踪染料经颅骨和颅内标记，并对表达光可转换荧光蛋白的脑膜和颅骨骨髓B细胞进行了光转化。我们还以特定部位的方式获得了耗尽B细胞的资源。通过这个实验性的“工具包”，我们现在的目标是解决脑膜B细胞和B细胞前体是直接来自头骨骨髓还是来自次级淋巴器官，以及它们从脑膜运输到哪里。然后，我们将通过经颅途径应用小分子抑制剂并将抗CD20B细胞耗竭抗体注射到枕大池，来测试脑膜B细胞在神经炎症中的功能相关性。最后，我们的目标是在深层转录特征中确定控制B细胞脑膜滞留的新机制。我们将使用体外‘翻转头骨’培养系统来验证新的候选基因，并可能在体内使用特定部位的抑制方法。因此，我们将研究脑膜成熟和祖细胞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.