Mechanisms of lymphocyte transmigration across the blood-brain barrier using an in vitro model that mimics blood flow and simulates inflammatory conditions as observed in the most frequent autoimmune disorder of the central nervous system, multiple sclero

多发性硬化症（MS）是一种常见的神经系统疾病，全世界约有200万人受到影响。自身反应性免疫细胞向中枢神经系统的浸润是其发病机制的关键步骤，因为这些细胞会对脑组织造成损伤。原理的证据来自像Natalizumab这样的药物，它可以阻止免疫细胞穿过血脑屏障（BBB），并为患者提供益处。然而，细胞在血脑屏障上的运输机制仍未完全解决。该计划的目的是更详细地研究细胞迁移。为此，Ransohoff博士和他的团队开发了一种体外血脑屏障模型，它很好地代表了体内情况。它包括人脑微血管内皮细胞的紧密单层，暴露于模拟炎症的细胞因子中。此外，剪切力被纳入模拟生理血流。先前使用该模型的实验室研究表明，单核细胞，而不是淋巴细胞，在遇到趋化因子CXCL12时，有效地粘附在发炎的内皮上，尽管这两种细胞类型都表达合适的趋化因子受体CXCR4 （Man S et al., 2012）。出乎意料的是，单核细胞阻滞引起了T细胞和B细胞的转移。我们假设单核细胞-内皮相互作用促进因子（趋化因子、细胞因子、蛋白水解酶）的分泌，使内皮表面允许与淋巴细胞相互作用。我们将检验这一假设，并使用我们创新的基于血流的体外血脑屏障模型来解决相关问题。首先，我们将检查单核细胞阻滞后内皮细胞的分子调节。接下来，我们将探讨这些单核细胞介导的内皮表面变化是否促进了淋巴细胞的转运。我们还考虑到淋巴细胞可能在没有单核细胞帮助的情况下能够转移，但有一种趋化因子选择性地向淋巴细胞发出信号。在我们的项目中，我们的目标是确定这种针对淋巴细胞的抑制趋化因子。此外，视频显微镜将用于可视化和表征流动中内皮细胞、单核细胞和淋巴细胞之间相互作用的动力学。这项研究的结果可能会为选择性治疗的发展提供新的视角，以防止MS中自身反应性免疫细胞的浸润。

Multiple sclerosis (MS) is a common neurological disease with about 2,000,000 people affected worldwide. The infiltration of autoreactive immune cells into the central nervous system is a crucial step in its pathogenesis as these cells cause injury to the brain tissue. Proof of principle comes from drugs like Natalizumab that prevent immune cells from crossing the blood-brain barrier (BBB) and provide benefit for patients. However, the mechanisms of cell trafficking across the BBB remain incompletely resolved. The aim of the proposed project is to study cellular transmigration in more detail. For that purpose, Dr. Ransohoff and his team have developed an in vitro model of the BBB which represents the in vivo situation very well. It comprises a tight monolayer of human brain microvascular endothelial cells which is exposed to cytokines that simulate inflammation. Further, shear forces are incorporated to mimic physiological blood flow. Previous studies in the lab using this model revealed that monocytes, but not lymphocytes, adhered efficiently on the inflamed endothelium upon encounter with the chemokine CXCL12 although both cell types expressed the appropriate chemokine receptor CXCR4 (Man S et al., 2012). Unexpectedly, monocyte arrest gave rise to the transmigration of T and B cells. We hypothesize that monocyte-endothelial interactions promote secretion of factors (chemokines, cytokines, proteolytic enzymes) which render the endothelial surface permissive for interaction with lymphocytes. We will test this hypothesis and address related questions using our innovative flow-based in vitro BBB model. First, we will examine molecular modulations of the endothelium after monocyte arrest. Next, we will ask whether those monocyte-mediated changes of the endothelial surface promote lymphocyte transmigration. We also take into account that lymphocytes may be capable to transmigrate without the help of monocytes but in the presence of a chemokine that selectively signals to lymphocytes. We aim to identify such an arrest chemokine specific for lymphocytes in our project. In addition, video microscopy will be used in order to visualize and characterize kinetics of interactions between endothelium, monocytes and lymphocytes under flow. Results arising from that research may reveal new perspectives on the development of selective therapeutics that prevent infiltration of autoreactive immune cells in MS.