Investigating the role of the actin cytoskeleton in regulating TLR-mediated B cell responses during inflammatory challenges

研究肌动蛋白细胞骨架在炎症挑战期间调节 TLR 介导的 B 细胞反应的作用

• 批准号: 336635366
• 负责人: Dr. Selina Keppler
• 金额: --
• 依托单位: Klinische Abteilung für Rheumatologie und Immunologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/336635366?language=en
• 关键词: Investigating; role; actin; cytoskeleton; regulating

B cells are a major regulator in maintaining immune homeostasis. Correct B cell activation is ensured by specific recognition of antigen by the B cell receptor (BCR) together with co-stimulation provided by activated T cells. Cytokine signalling or the engagement of Toll-like receptors (TLR) also influence B cell function. Aberrant B cell activation might lead to the development of autoimmune diseases, as seen in Wiskott-Aldrich Syndrome (WAS). WAS is an immunodeficiency associated with high levels of IgA and IgE antibodies, increased susceptibility to infections and heightened risk of immune-mediated disorders, including colitis. Cause of disease are genetic mutations leading to defective expression of the WAS protein (WASP) or the WASP interacting protein (WIP), both regulators of the actin cytoskeleton. B cells deficient for WASP or WIP are hyper-proliferative to both BCR and TLR signalling, as we and others recently demonstrated. With the here described project, we wish to understand and further elucidate the role of those actin regulators in TLR signalling in the context of inflammation. Preliminary findings for this grant application show that in response to TLR4 stimulation in vitro, B cells deficient in WIP (WIP KO) secrete high amounts of the pro-inflammatory cytokines IL-6 and TNF-a. Concomitantly, WIP KO B cells show a diminished expression of the plasma cell specific transcription factor (TF) IRF4 and also of the TF T-bet, which might influence antibody and cytokine production. Pro-inflammatory cytokines can become self-destructive in the acute setting of sepsis or in response to the commensal microbiota. Our preliminary results indeed show an increased B cell activation and IgA production in the gut of non-immunised WIP KO mice, and an early onset of colitis in chimeras in which only B cells lack WIP. Thus, a defective differentiation into plasma cells together with an increased IL-6 and TNF-a production by B cells might ultimately enhance the autoimmune phenotype in WAS. We therefore hypothesize that in B cells WIP is involved in the modulation of signalling pathways regulating TF expression, antibody production and cytokine secretion after TLR4 engagement thereby influencing immune homeostasis in the gut. To test this hypothesis, we plan to (1) analyse the role of the actin regulators WIP and WASP in TLR4 signal induction, endocytosis, cytokine and antibody production of B cells in vitro and in vivo, (2) analyse the underlying molecular mechanism determining TF expression and B cell fate decision and (3) analyse the in vivo impact of the imbalanced cytokine production, plasma cell differentiation and IgA antibody secretion of WIP KO B cells during sepsis and the onset of colitis. By investigating these aims, we will gain further understanding of autoimmune diseases like WAS which may be useful for the development of novel treatment options, not only in WAS but also other immune-related disorders, like inflammatory bowel disease.

B细胞是维持免疫稳态的主要调节因子。正确的B细胞活化通过B细胞受体（BCR）对抗原的特异性识别以及活化的T细胞提供的共刺激来确保。细胞因子信号传导或Toll样受体（TLR）的参与也影响B细胞功能。异常的B细胞活化可能导致自身免疫性疾病的发展，如Wiskott-Aldrich综合征（WAS）。WAS是一种免疫缺陷，与高水平的伊加和IgE抗体，增加感染的易感性和免疫介导的疾病，包括结肠炎的风险增加。疾病的原因是基因突变导致WAS蛋白（WASP）或WASP相互作用蛋白（WASP interacting protein，WASP interacting protein，WASP）表达缺陷，这两种蛋白都是肌动蛋白细胞骨架的调节因子。正如我们和其他人最近所证明的，WASP或THP缺陷的B细胞对BCR和TLR信号传导都是过度增殖的。通过这里描述的项目，我们希望了解并进一步阐明这些肌动蛋白调节剂在炎症背景下TLR信号传导中的作用。该资助申请的初步发现显示，在体外响应于TLR 4刺激，缺乏IL-10的B细胞（IL-10 KO）分泌大量的促炎细胞因子IL-6和TNF-α。伴随地，MAPKO B细胞显示浆细胞特异性转录因子（TF）IRF 4以及TF T-bet的表达减少，这可能影响抗体和细胞因子的产生。促炎细胞因子在脓毒症的急性环境中或响应于肠道微生物群可以变得自我破坏。我们的初步结果确实显示了在非免疫的RIKO小鼠的肠道中增加的B细胞活化和伊加产生，以及在只有B细胞缺乏IgA的嵌合体中结肠炎的早期发作。因此，向浆细胞的分化缺陷以及B细胞产生的IL-6和TNF-α的增加可能最终增强WAS中的自身免疫表型。因此，我们假设在B细胞中，TLR 4参与调节TF表达、抗体产生和细胞因子分泌的信号传导途径的调节，从而影响肠道中的免疫稳态。为了验证这一假设，我们计划（1）分析肌动蛋白调节因子β 1和WASP在体外和体内B细胞的TLR 4信号诱导、内吞作用、细胞因子和抗体产生中的作用，（2）分析决定TF表达和B细胞命运决定的潜在分子机制，以及（3）分析不平衡的细胞因子产生的体内影响，脓毒症和结肠炎发作期间，CD 4KO B细胞的浆细胞分化和伊加抗体分泌。通过研究这些目标，我们将进一步了解WAS等自身免疫性疾病，这可能有助于开发新的治疗方案，不仅适用于WAS，还适用于其他免疫相关疾病，如炎症性肠病。