Microbial sensing and innate immune activation in B cells

B 细胞中的微生物传感和先天免疫激活

• 批准号: RGPIN-2020-06330
• 负责人: Stager, Simona
• 金额: $ 2.33万
• 依托单位: Institut national de la recherche scientifique
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=740751
• 关键词: Microbial; sensing; innate; immune; activation

B-cells are mostly known for their capacity to produce antibodies. However, an increasing body of literature has now shown that they may also participate in the immune response by various antibody-independent mechanisms, such as cytokine production, co-stimulation, and antigen presentation. B-cells can be divided in three different subpopulations: follicular B cells , innate-like marginal zone B-cells (MZB), and B1 B-cells. Follicular B cells are the most prominent B-cell subpopulation and reside in lymphoid follicles of secondary and tertiary lymphoid organs. MZB are located in the marginal zone of the spleen and are endowed with the capacity to bind immune complexes, migrate towards the splenic white pulp, and transfer antigen to follicular dendritic cells. B1 B-cells are known for their secretion of natural antibodies. We have recently reported that B cells can capture the protozoan parasite Leishmania donovani. Upon exposure to the parasite, B cells form clusters and hold L. donovani in extracellular IgM-rich pockets. This close interaction results in polyclonal B cell activation and eventually in cell death after 24-48h. Interestingly, the parasite triggers endosomal Toll-Like Receptors (TLRs), although it is attached extracellularly on the cell surface of the B cell. Activation of endosomal TLRs was required to induce IL-10 and IFN-I expression and to promote hypergammaglobulinemia. The pathways up- and downstream of endosomal TLR activation in B-cells and the contribution of these pathways to the induction of hypergammaglobulinemia are as yet unknown. Definition of these steps will require a deeper understanding of how B cells interact with the parasite. The overall goal of our research is to understand how various B cell subpopulations recognize and react to microorganisms, and how this recognition affects their function. Our objective in this application is to characterize the interaction between L. donovani and B cells in order to understand pathways leading to polyclonal B cell activation. Particularly, we will investigate i) parasite capture and cell surface interaction between L. donovani and various B cell subpopulations; ii) parasite recognition by endosomal toll-like receptors and other microbial sensors (mainly cytosolic) and the downstream pathways they activate; and iii) cell-to-cell communication (e.g. tunnelling nanotubules; receptor/ligand interactions) and role of this communication in the induction of polyclonal B cell activation. Transgenic parasites, knock-out mice, confocal microscopy, flow cytometry, and several biochemical techniques will be used to dissect the various activation and cellular communication pathways in in vitro experiments. The pathways identified here could uncover novel strategies that may also be used by other microorganisms to activate B cells and modulate their functions.

B细胞主要以产生抗体的能力而闻名。但是，越来越多的文献已经表明，它们也可能通过各种抗体独立的机制（例如细胞因子的产生，共刺激和抗原表现）参与免疫响应。 B细胞可以分为三种不同的亚群：卵泡B细胞，先天性边缘区B细胞（MZB）和B1 B细胞。卵泡B细胞是最突出的B细胞亚群，驻留在二级和三级淋巴机构的淋巴四四形。 MZB位于脾脏的边际区域，并具有结合免疫复合物，朝着脾白浆中迁移并将抗原转移到卵泡树突状细胞的能力。 B1 B细胞以其天然抗体的分泌而闻名。我们最近报告说，B细胞可以捕获原生动物寄生虫Donovani。暴露于寄生虫后，B细胞会形成簇，并在细胞外IgM富含的口袋中固定L. donovani。这种紧密的相互作用导致多克隆B细胞的激活，最终在24-48h后最终导致细胞死亡。有趣的是，寄生虫会触发内体收费受体（TLR），尽管细胞外附着在B细胞的细胞表面上。需要内体TLR的激活来诱导IL-10和IFN-I表达并促进高γ-全脂血症。 B细胞中内体TLR激活的上下途径，以及这些途径对诱导高γ-全脂血症的贡献尚不清楚。这些步骤的定义将需要更深入地了解B细胞如何与寄生虫相互作用。我们研究的总体目标是了解各种B细胞亚群如何识别和反应微生物，以及这种识别如何影响其功能。我们在此应用中的目标是表征多诺瓦尼乳杆菌和B细胞之间的相互作用，以便理解导致多克隆B细胞激活的途径。特别是，我们将研究i）多诺瓦尼乳杆菌与各种B细胞亚群之间的寄生虫捕获和细胞表面相互作用； ii）内体电话样受体和其他微生物传感器（主要是胞质）及其激活的下游途径的寄生虫识别；和iii）细胞对细胞通信（例如隧道纳米管；接收器/配体相互作用）以及这种通信在诱导多克隆B细胞激活中的作用。转基因寄生虫，敲除小鼠，共聚焦显微镜，流式细胞术和几种生化技术将用于在体外实验中剖析各种​​激活和细胞通信途径。这里确定的途径可能会发现新的策略，其他微生物也可以使用这些策略来激活B细胞并调节其功能。