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2，000，000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中的关键步骤，因为这些细胞导致脑组织损伤。原理的证据来自Natalizumab等药物，这些药物可以防止免疫细胞穿过血脑屏障（BBB）并为患者提供益处。然而，穿过BBB的细胞运输的机制仍然没有完全解决。该项目的目的是更详细地研究细胞的迁移。为此，Ransohoff博士和他的团队开发了一种BBB的体外模型，该模型非常好地代表了体内情况。它包括暴露于模拟炎症的细胞因子的紧密单层人脑微血管内皮细胞。此外，结合剪切力以模拟生理血流。在实验室中使用该模型的先前研究揭示，单核细胞而不是淋巴细胞在遇到趋化因子CXCL 12时有效地粘附在发炎的内皮上，尽管两种细胞类型都表达适当的趋化因子受体CXCR 4（Man S等人，2012年）。出乎意料的是，单核细胞停滞引起T和B细胞的迁移。我们假设单核细胞-内皮细胞相互作用促进因子（趋化因子、细胞因子、蛋白水解酶）的分泌，这些因子使内皮细胞表面允许与淋巴细胞相互作用。我们将使用我们创新的基于血流的体外血脑屏障模型来检验这一假设并解决相关问题。首先，我们将研究单核细胞停滞后内皮细胞的分子调节。接下来，我们将探讨单核细胞介导的内皮细胞表面变化是否促进淋巴细胞的迁移。我们还考虑到淋巴细胞可能能够在没有单核细胞的帮助下，但在存在选择性地向淋巴细胞发出信号的趋化因子的情况下迁移。我们的目标是在我们的项目中确定这样一种对淋巴细胞特异的趋化因子。此外，将使用视频显微镜观察和表征血流条件下内皮细胞、单核细胞和淋巴细胞之间相互作用的动力学。该研究的结果可能揭示了预防MS中自身反应性免疫细胞浸润的选择性治疗方法的发展的新观点。

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.