Defective Ca2+ signalling between B cells and regulatory T cells: connecting the dots in the emergence of impaired peripheral B cell tolerance in multiple sclerosis?

本研究旨在促进我们对多发性硬化症(MS)致病B细胞调控的分子机制的理解。多发性硬化症是一种自身免疫介导的中枢神经系统(CNS)脱髓鞘疾病。最近的证据表明，外周B细胞耐受性受损是MS患者致病B细胞频率升高的原因，这可能是由于T细胞非依赖性过程中B细胞调节的异常，或者通过调节性T细胞(Tregs)介导的T细胞依赖性过程。正如我们和其他人之前已经证明的那样，多发性硬化症患者的Treg功能存在缺陷。它们抑制性的丧失是由于幼稚细胞的收缩和外周Treg细胞隔间记忆表型的相互扩张，而这可能是由于过早的免疫衰老引起的。目前，关于B细胞是否是Tregs的直接靶点，以及它们如何实现抑制B细胞效应功能，如免疫球蛋白的产生、抗原递呈和细胞因子的分泌，人们知之甚少。此外，虽然已知通过B细胞调节效应性T细胞的反应，但B细胞是否也影响Treg活性的问题尚未解决。由于两个细胞亚群之间双向相互作用的任何损害都可能对MS患者的自身免疫反应产生有害影响，我们的目标是更详细地分析B细胞和Tregs之间的串扰。我们打算使用单个细胞的实时成像来测量Tregs调节周围不同表型B细胞中钙信号的能力，这是Tregs用来抑制传统T细胞(Tcons)的关键机制，正如我们之前所展示的那样。成像实验将通过评估钙离子振荡模式和钙离子驱动的B细胞激活下游事件之间的相关性来补充。补充性实验旨在阐明B细胞是否直接影响Tregs的功能能力。

The present proposal intends to advance our understanding of the molecular mechanisms regulating the control of pathogenic B cells in multiple sclerosis (MS), an autoimmune-mediated demyelinating disorder of the central nervous system (CNS). Recent evidence has revealed that an impaired peripheral B cell tolerance accounts for heightened frequencies of pathogenic B cells in patients with MS. This might arise through aberrations in B cell regulation from T cell-independent processes, or through T cell-dependent processes mediated by regulatory T cells (Tregs). Tregs are functionally deficient in patients with MS as we and others have previously shown. Their loss of suppressive properties is precipitated by a contraction of naive cells and reciprocal expansion of memory phenotypes in the peripheral Treg cell compartment, which in turn, possibly arises from premature immunosenescence. At present, little is known as to whether B cells are direct targets of Tregs and how they achieve suppression of B cell effector functions such as immunoglobulin production, antigen presentation, and cytokine secretion. Furthermore, while Modulation of effector T cell responses through B cells is known to occur, the question whether B cells also impact Treg activity has not been addressed. Since any impairment in the bi-directional interaction between the two cell subsets might have harmful consequences on developing autoimmune responses in patients with MS, we aim to analyze the cross-talk between B cells and Tregs in more detail. We intend to employ live Imaging of single cells to measure the capacity of Tregs to modulate Ca2+ signaling in surrounding B cells of various phenotypes, which is a key mechanism utilized by Tregs to confer suppression in conventional T cells (Tcons) as we have previously shown. The imaging experiments will be complemented by assessing the correlation between Ca2+ oscillation patterns and Ca2+-driven downstream events of B cell activation. Complementary experiments aim to clarify whether B cells directly influence the functional capacity of Tregs.