Regulation of GC B Cells by Transcription Factor STAT3

 描述(申请人提供)：生发中心(GC)是独特的微环境，具有增殖的B细胞经历类别转换，体细胞肥大和亲和力成熟。尽管存在其他途径，但GC是长寿抗体(Ab)分泌浆细胞和记忆B细胞的主要来源。先前的研究表明，系统性红斑狼疮可能是由于GC活性增强而发生的。在狼疮易感小鼠体内发现了自发的GC形成。此外，活动期狼疮患者GC反应异常，浆细胞增多。因此，了解调控GC形成和GC B细胞分化的信号通路可能为SLE的成功干预找到新的靶点。信号转导和转录因子激活因子3(STAT3)信号通路是人类B细胞分化为分泌抗体的浆细胞的关键。STAT3通路的失调也参与了SLE的发生发展。然而，STAT3在GC B细胞反应中的作用一直存在争议。先前的一项研究表明，B细胞特异性STAT3缺陷小鼠具有较低的T依赖性免疫球蛋白应答，但显示正常的GC形成。自相矛盾的是，GC是记忆B细胞和长寿浆细胞的主要来源。这项研究的一个警告是，他们只在第12天检查GC反应。我们的初步研究表明，B细胞特异性STAT-3KO小鼠在后期(第21天和第28天)显著减少GC形成、GC B细胞和TFH细胞，但在早期(第7天和第12天)没有。此外，STAT3缺陷的自身反应性B细胞在免疫后具有缺陷的自身抗体反应和GC B细胞分化。我们推测，STAT3信号对于维持GC的形成和GC B细胞的分化是必不可少的。针对这一假设，本文提出了两个目标。目的1确定STAT3信号调节GC形成和GC B细胞反应的机制。我们将检验STAT3信号对GC B细胞生存的影响这一假设。需要STAT3信号的GC B细胞分化的特定阶段将被确定。目的2研究在狼疮易感的MRL/LPR小鼠模型中，B细胞固有的STAT3信号是否参与自身抗体的产生和疾病的进展。此外，我们还将使用抗CD19单链可变区(ScFv)微型抗体将STAT3 siRNA特异性地运送到MRL/LPR小鼠的B细胞中。这种干预的治疗效果将被确定。这项建议的总体目标是确定STAT3信号如何调节GC的形成和GC B细胞的反应，以及在自身反应性B细胞中去除STAT3信号是否有利于狼疮的治疗。

 DESCRIPTION (provided by applicant): Germinal centers (GCs) are unique microenvironment that has proliferative B cells undergoing class switching, somatic hypermuation, and affinity maturation. Although alternative pathways exist, GCs are the major source of long-lived antibody (Ab)-secreting plasma cells and memory B cells. Previous studies have demonstrated that SLE may develop as a result of enhanced GC activity. Spontaneous GC formation has been found in the lupus-prone mice. In addition, active lupus patients have abnormal GC reactions and increased plasma cells. Therefore, understanding signaling pathways that regulate the GC formation and GC B cell differentiation may identify novel targets for the successful intervention of SLE. The signal transducer and activator of transcription factor 3 (STAT3) signaling pathway is critical for human B cells to differentiate into Ab-secreting plasma cells. Dysregulation of STAT3 pathway has also been implicated in the development of SLE. However, the role of STAT3 in the GC B cell response has been controversial. A previous study has demonstrated that B cell-specific STAT3 deficient mice have lower T- dependent IgG response but display normal GC formation. Paradoxically, GC is the major source of both memory B cells and long-lived plasma cells. One caveat of this study is that they only examined GC response at day 12. Our preliminary studies demonstrated that B cell-specific STAT-3 KO mice had significantly decreased GC formation, GC B cells, and Tfh cells in the later phase (days 21 and 28) but not in the early time point (days 7 and 12). Furthermore, STAT3-deficient autoreactive B cells had defective autoAb responses and GC B cell differentiation upon immunization. We hypothesize that STAT3 signaling is essential for the maintenance of the GC formation and GC B cell differentiation. Two Aims are proposed to address this hypothesis. Aim 1 determines the mechanisms by which STAT3 signaling regulates the maintenance of the GC formation and GC B cell response. We will test the hypothesis that STAT3 signaling is required for the GC B cell survival. The specific stage of GC B cell differentiation that requires STAT3 signaling will be determined. Aim 2 examines whether B cell intrinsic STAT3 signaling is required for autoAb production and disease progression in lupus-prone MRL/lpr mouse model. In addition, we will use anti-CD19 single chain variable fragment (scFv) miniAb to specifically deliver STAT3 siRNA into B cells in MRL/lpr mice. The therapeutic efficacy of this intervention will be determined. The overall goal of this proposal is to determine how STAT3 signaling regulates the GC formation and GC B cell response and whether ablation of STAT3 signaling specifically in autoreactive B cells provides benefit for lupus treatment.