Regulation of GC B Cells by Transcription Factor STAT3

 描述（由申请人提供）：老年中心（GC）是具有经历类别转换、体细胞超突变和亲和力成熟的增殖性B细胞的独特微环境。虽然存在替代途径，但GC是长寿命抗体（Ab）分泌浆细胞和记忆B细胞的主要来源。以往的研究表明，SLE的发展可能是GC活性增强的结果。在狼疮易感小鼠中发现了自发GC形成。此外，活动性狼疮患者有异常的GC反应和浆细胞增加。因此，了解调控GC形成和GC B细胞分化的信号通路可能为成功干预SLE确定新的靶点。 信号转导和转录激活因子3（STAT 3）信号通路是人B细胞向分泌Ab的浆细胞分化的关键。STAT 3通路的失调也与SLE的发展有关。然而，STAT 3在GC B细胞应答中的作用一直存在争议。先前的研究已经证明，B细胞特异性STAT 3缺陷小鼠具有较低的T依赖性IgG应答，但显示正常的GC形成。巧合的是，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，他们只检查了第12天的GC反应。我们的初步研究表明，B细胞特异性STAT-3 KO小鼠在晚期（第21天和第28天）具有显著降低的GC形成、GC B细胞和Tfh细胞，但在早期时间点（第7天和第12天）没有。此外，STAT 3缺陷型自身反应性B细胞在免疫后具有缺陷型自身抗体应答和GC B细胞分化。我们推测STAT 3信号通路对于维持GC形成和GC B细胞分化是必不可少的。提出了两个目标来解决这个假设。目的1明确STAT 3信号通路调控GC形成和GC B细胞应答的机制。我们将检验STAT 3信号传导是GC B细胞存活所必需的这一假设。将确定需要STAT 3信号传导的GC B细胞分化的特定阶段。目的2在狼疮易感MRL/lpr小鼠模型中检查B细胞内在STAT 3信号传导是否是自身抗体产生和疾病进展所需的。此外，我们将使用抗CD 19单链可变片段（scFv）miniAb将STAT 3 siRNA特异性地递送到MRL/lpr小鼠的B细胞中。将确定这种干预的治疗效果。该提案的总体目标是确定STAT 3信号传导如何调节GC形成和GC B细胞应答，以及在自身反应性B细胞中特异性地消融STAT 3信号传导是否为狼疮治疗提供益处。

 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.