下调Bcl-6抑制滤泡辅助性T细胞抗cGVHD的作用机制研究

Chronic graft-versus-host disease (cGVHD) is the most serious complication of allogeneic hematopoietic stem cell transplantation (Allo-HSCT), which is the syndrome resembling autoimmune disorders, and significant negative impacts on patient survival and quality of life. The effectiveness of management strategies beyond systemic corticosteroids is controversial. Current therapies for chronic GVHD are targeted primarily and non-specifically against donor T-cell activity or depleted B-cells. These non-targeted therapies lead to malignancy relapse, severe infection ,secondary tumor or refractory cGVHD, so explore target therapies for cGVHD is urgent in the future. Follicular helper T cells (Tfh) is a new member of CD4+ T cells subgroup, and it was recently confirmed that its differentiation, proliferation, and auxiliary process of B cell disorders, were closely associated with autoimmune disease. However, less studies have addressed the functional role of Tfh cells in development of chronic graf-versus-host disease (cGVHD), which is related to B cell disorder. Bcl-6 has been identified as a master regulator of Tfh, which regulates Tfh differentiation and proliferation, GC formation and B cell helpering in vivo. At the same time, IL-21 as a critical effector factor of Tfh cells has been established. We observed that the expression of STAT3 and IL-21R which modulates the Bcl-6 expression were upregulated in activated cGVHD patients by expression profile chip, and the B cell turbulence was recovered when the cGVHD improvement. Our studies suggest that the perturbation of Bcl-6 signaling on Tfh cells may provide a new approach for GVHD treatment. Understanding the role of Tfh and the related mechanism of CD4+ T cells subgroup in the pathogensis of chronic GVHD, and target blocking Bcl-6 to inhibit Tfh differentiation and functions may allow us to develop new targeted therapeutic approaches that limit non-specifical immune suppression and improve both disease-related and treatment-related outcomes.

滤泡辅助性T（Tfh）细胞是B细胞最重要的辅助细胞，其分化增殖失控及辅助B细胞功能紊乱致自身免疫疾病的发生。抑制Tfh对B细胞功能紊乱相关的慢性移植物抗宿主病（cGVHD）的作用如何？目前国内外尚未见报道。Bcl-6是Tfh分化、功能实施的特异性转录子，而IL-21是Tfh的关键效应分子。前期我们通过表达谱芯片发现cGVHD患者高表达Bcl-6调节基因STAT3及IL-21R，而且随病情好转，B细胞紊乱得以恢复。因此，我们提出特异性阻断Bcl-6抑制Tfh可能是cGVHD防控的新靶点。本研究拟通过Bcl6-RFP reporter小鼠cGVHD模型，观察性特异性阻断Bcl-6，对cGVHD、Tfh、其他CD4+T亚群及相关分子的影响；监测Tfh、Bcl-6与临床cGVHD的相关性，探讨Bcl-6调控Tfh在cGVHD中的作用及相关机制，为cGVHD靶向治疗及早期诊断提供依据。

滤泡辅助性T（Tfh）细胞是B细胞最重要的辅助细胞，其分化增殖失控及辅助B细胞功能紊乱致自身免疫疾病的发生。Bcl-6是Tfh分化、功能实施的特异性转录子，而IL-21是Tfh的关键效应分子。前期我们通过表达谱芯片发现cGVHD患者高表达Bcl-6调节基因STAT3及IL-21R，而且随病情好转，B细胞紊乱得以恢复。本研究我们提出特异性阻断Bcl-6抑制Tfh可能是cGVHD防控的新靶点。本研究体内外实验应用Bcl6小分子抑制剂可下调Bcl6，抑制滤泡辅助性T细胞的表达，进而抑制B细胞向浆细胞分化。体外下调BCL6基因的表达，对T细胞极化的影响主要表现为抑制Tfh细胞的表达，79-6干预组组中，B细胞也相应降低。79-6治疗小鼠cGVHD 取得初步疗效，临床表现为脱毛减少、气促好转、活力恢复、体重上升；治疗的主要效应靶器官为皮肤和肺脏，其机制与79-6 下调BCL-6表达，抑制Tfh细胞辅助B细胞分泌功能相关。Bcl6 可作为cGVHD 免疫治疗新靶点，对于推进临床疾病精准治疗具有重要意义。监测患者体内Tfh、Bcl-6，进一步验证前期研究发现，cGVHD 患者体内存在Tfh比例失衡，cGVHD 的发生与tfh17亚群的表达升高有关，动态监测tfh表达水平的变化有可能为临床早期诊断慢性移植物抗宿主病或预测其发生提供参考，可望成为一个新的分子标记物应用于临床诊疗。