Antigen-presenting and phagocytic functions of B cell subsets

b细胞以其产生抗体的能力而闻名。然而，越来越多的文献表明，它们也可能通过各种抗体独立机制参与免疫应答，如细胞因子产生、共刺激和抗原呈递。B细胞可分为三个不同的亚群：滤泡B细胞或B2细胞，先天样边缘带B细胞（MZB）和B1 B细胞。滤泡B细胞是最重要的B细胞亚群，存在于二级和三级淋巴器官的淋巴滤泡中。MZB位于脾脏边缘区，具有结合免疫复合物、向脾白髓迁移、将抗原转移到滤泡树突状细胞的能力。B1 b细胞以分泌天然抗体而闻名。*******我们最近报道了B细胞可以捕获原生动物寄生虫多诺瓦利什曼原虫。暴露于寄生虫后，B细胞形成簇状并将L. donovani寄生虫保存在富含igm的口袋中。这种密切的相互作用导致共刺激分子CD86和表面IgM的上调，在myd88依赖性IL-10的产生中，最终导致48h后细胞死亡。MyD88是大多数toll样受体（TLRs）使用的一种适配器蛋白，用于激活转录因子NFk-B和转录因子IRF家族。b细胞MyD88激活的上游途径尚不清楚。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病原体，以及这种识别如何影响它们的功能。我们在这个应用程序的目的是表征L. donovani和B细胞之间的相互作用，以了解多克隆B细胞的激活途径。特别是，我们将研究i)各种toll样受体、补体受体和B细胞受体对寄生虫的识别，以及激活的下游途径；Ii)寄生虫衍生抗原的抗原呈递；iii)寄生体捕获及与不同B细胞亚群的表面相互作用。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在体外实验中用于解剖各种激活途径。*******这里发现的激活途径可能揭示新的策略，也可能被其他病原体用于激活B细胞并调节其功能

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 or B2 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 parasites in IgM-rich pockets. This close interaction results in the upregulation of the costimulatory molecule CD86 and of surface IgM, in a MyD88-dependent IL-10 production, and eventually in cell death after 48h. MyD88 is an adapter protein used by most Toll-Like Receptors (TLRs) to activate the transcription factors NFk-B and the IRF family of transcription factors. The pathways upstream of MyD88 activation in B-cells 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 pathogens, 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 the pathways of polyclonal B cell activation. Particularly, we will investigate i) parasite recognition by various toll-like receptors, complement receptors, and the B cell receptor, and the activated downstream pathways; ii) antigen-presentation of parasite-derived antigens; and iii) parasite capture and surface interaction between L. donovani and various B cell subpopulations. Transgenic parasites, knock-out mice, confocal microscopy, flow cytometry, and several biochemical techniques will be used to dissect the various activation pathways in in vitro experiments.*******The activation pathways identified here could uncover novel strategies that may also be used by other pathogens to activate B cells and modulate their functions.***