LAIR-1在幽门螺杆菌逃逸宿主免疫应答中的作用研究

Helicobacter pylori (H. pylori) can escape the host immune response, but the mechanism has not been clarified. The newly discovered molecular LAIR-1 can specifically combine with collagen, the high affinity ligand of H. pylori and then can be coaggregated on the cell surface. LAIR-1 could recruits SHP-1 through its two ITIM motif in the cytoplasmic region and inhibits the transduction of the downstream activating signals in effect cells, thus inhibit the immune system. Our preliminary results show that H. pylori cocultured with U937 cells may lead to an increase secretion of LAIR-1 and with the increasing ratio between H. pylori and cells, the expression of LAIR-1 raised. This project is intended to use ELISA, RT-PCR, Western Blot and Flow Cytometry to study the influence of H. pylori on the expression of LAIR-1 on monocytes. Then, use siRNA, cell transfection and targeted signal pathway blocking method, to investigate the role of LAIR-1 in the immune escape of H. pylori and related signal pathways with the participation of SHP-1. The project is going to clarify a novel mechanism of H. pylori how to escape the host immune response and provide a new idea for the prevention of H. pylori infection.

幽门螺杆菌(H.pylori)可逃逸宿主免疫应答，但其机制尚未明确。新发现的免疫抑制性分子LAIR-1可与胶原(H.pylori的高亲和力配体)特异性结合并发生聚集，聚集后的LAIR-1通过胞浆区两个ITIM基序募集SHP-1而抑制效应细胞激活信号的转导。我们前期研究发现，H.pylori与U937细胞相互作用可导致后者LAIR-1的分泌增加，并且LAIR-1的表达水平随着H.pylori与细胞比例的增加而有所升高。本项目拟在前期研究基础上，采用ELISA、RT-PCR、Western Blot、流式细胞术等技术研究H.pylori对LAIR-1分子在单核细胞、胃黏膜上皮细胞中表达的影响；通过RNA干扰、细胞转染及靶向阻断信号通路等方法研究LAIR-1募集SHP-1参与的相关信号通路，以期阐明H.pylori逃逸宿主免疫应答的新机制，为H.pylori感染的防治提供新思路。

幽门螺杆菌逃逸宿主免疫应答的机制尚未明确。本项目通过幽门螺杆菌与单核细胞THP-1 共培养，流式细胞术检测细胞凋亡及LAIR-1蛋白的表达；幽门螺杆菌菌液灌胃建立小鼠感染模型，流式细胞术检测小鼠外周血单个核细胞（PBMC）中单核细胞和淋巴细胞表面LAIR-1的表达；采用LAIR-1沉默的THP-1细胞，检测幽门螺杆菌诱导的细胞凋亡、细胞增殖、IL-8、IL-10和细胞内信号激活情况。. 幽门螺杆菌可显著下调THP-1细胞LAIR-1的表达，参与诱导其细胞凋亡，LAIR-1可能与单核细胞凋亡有关。幽门螺杆菌感染下调小鼠PBMC中单核细胞及LAIR-1的表达，上调淋巴细胞比例但下调其LAIR-1的表达。幽门螺杆菌感染后THP-1细胞凋亡、增殖、IL-8、IL-10升高。LAIR-1沉默明显抑制幽门螺杆菌感染后THP-1中IkBa、eIF2a、JNK、Smad2的磷酸化。无论THP-1细胞是否感染幽门螺杆菌，对照组和LAIR-1组siRNA的增殖率均无显著差异。LAIR-1可调节THP-1细胞的凋亡和炎症因子分泌，有助于维持炎症反应，防止幽门螺杆菌被免疫反应清除。初步明确了LAIR-1在幽门螺杆菌逃逸宿主免疫应答中的作用，为幽门螺杆菌感染的防治提供了新思路。