滤泡辅助性T细胞在不明原因复发性流产中的作用及分子机制

As a novel subset of CD4+ T cells, T follicular helper cells (Tfh) play a key role in providing help for B cell proliferation, differentiation and antibody production. Although the dysregulations of Tfh-cell number and function have been demonstrated to be closely correlated with a variety of diseases, the role and underlying molecular mechanisms of Tfh cells on normal pregnancy and pregnancy-associated diseases have never been reported. In our previous study, we found that there were a large number of Tfh cells accumulated in the uterine decidua and the proportion of splenic Tfh cells in spontaneous abortion mice was significantly lower than that in normal group at the mid-pregnancy. In this project, we will investigate the role of Tfh cells in unexplained recurrent spontaneous abortion (URSA) by comparing the Tfh cells between spontaneous abortion and normal pregnancy (including mice model and human samples), and analyzing the reproductive capacity, B cell maturation and antibody production after receiving Tfh cells in spontaneous abortion mice; and afterwards, we will investigate the underlying molecular mechanisms by determining whether their role is dependent on IL-21 secretion, Bcl-6/Blimp-1 balance and ICOS/ICOSL interaction (including in vivo and in vitro study). This study will lay a foundation for our further understanding of maternal-fetal recognition and immune tolerance, as well as for the treatment of URSA patients.

作为一种新型CD4+ T细胞亚群，滤泡辅助性T细胞（Tfh）在辅助B细胞增殖、分化和抗体产生中起关键作用。研究证实Tfh细胞的数量及功能紊乱与多种疾病的发生密切相关，然而其在正常妊娠及妊娠相关疾病中的作用和机制尚无报道。我们的前期研究发现孕中期正常妊娠小鼠子宫蜕膜中存在大量的Tfh细胞，并且流产组脾脏中Tfh细胞的比例显著低于正常妊娠组。本项目将通过进一步比较不明原因复发性流产和正常妊娠组（包括小鼠模型和人群样本）Tfh细胞的差异，以及过继转移Tfh细胞对小鼠生殖能力、B细胞成熟和抗体产生的影响等方面系统解析Tfh细胞在不明原因复发性流产中的作用，并对其作用是否依赖于IL-21分泌、Bcl-6/Blimp-1平衡以及ICOS/ICOSL相互作用等进行深入研究（包括体内和体外实验），以探讨其分子机制。该研究对深入理解妊娠母-胎识别和免疫耐受机理以及不明原因复发性流产的治疗具有重要的指导意义。

前期研究发现，滤泡辅助性T细胞（Tfh）细胞的数量及功能紊乱与多种疾病的发生密切相关，然而其在正常妊娠及妊娠相关疾病中的作用与机制尚无报道。本项目的主要研究内容包括应用小鼠模型系统解析CD4+CXCR5hiPD-1hi Tfh细胞在不明原因复发性流产（URSA）中的作用与分子机制，以及应用high-throughput mRNA-Seq技术深度解析孕早期健康妊娠妇女蜕膜CD4+ (dCD4) T细胞的转录组和可变剪切（AS）图谱。.我们的研究发现：（1）正常妊娠小鼠孕中期子宫蜕膜中存在大量的CD4+CXCR5hiPD-1hi Tfh细胞，高表达Bcl-6同时具有memory/activation表型，并且该细胞的比例与胚胎吸收率成负相关；（2）URSA小鼠脾脏中CD4+CXCR5hiPD-1hi Tfh细胞的比例显著低于正常妊娠组;（3）小鼠体内注射PD-L1功能性阻断抗体能够诱发早期自然流产，从而说明母—胎免疫耐受的建立和正常妊娠的维持需要PD-1/PD-L1信号转导；（4）妊娠早期子宫蜕膜CD4+CXCR5hiPD-1hi Tfh细胞的增加与抗PD-L1诱发自然流产的发生密切相关。以上结果首次提示蜕膜CD4+CXCR5hiPD-1hi Tfh细胞的增加与母—胎免疫耐受紊乱以及URSA发生密切相关；（5）与自体外周血CD4+ (pCD4) T细胞相比，人孕早期蜕膜CD4+ (dCD4) T细胞具有完全不同的转录组和可变剪切（AS）图谱。.以上研究成果已经发表标注项目编号（81501333）的SCI论文11篇，包括著名的Frontiers in Immunology、Molecular Therapy-Nucleic Acids 和Cell Death and Disease等杂志。此外，项目负责人应邀在中国免疫学会第十一和十三届全国免疫学学术大会上做口头报告（分会场交流）。