艰难梭菌毒素蛋白B刺激巨噬细胞产IL-1β是引发宿主肠道炎症风暴的关键。IL-1β由pro -IL-1β经切割产生。毒素B可促进pro-IL-1β的产生，但其机制不明。我们前期结果显示：毒素B通过活化p38MAPK信号通路促进pro-IL-1β产生，此过程依赖经典接头蛋白MyD88；FZD5作为可能的巨噬细胞表面毒素B受体，在毒素B刺激下可与MyD88结合。因此我们推测：毒素B可能与FZD5或其他受体结合，招募MyD88，进而活化下游信号通路促进pro-IL-1β产生。本课题首先验证MyD88对pro-IL-1β形成的作用，采用免疫共沉淀与荧光共定位技术研究MyD88和受体的相互作用，构建受体敲除细胞株以明确受体的功能，最终通过体内外实验揭示毒素蛋白B促巨噬细胞产pro-IL-1β的机制。本课题对进一步了解艰难梭菌在肠炎中的致病机制、寻找艰难梭 菌肠炎的免疫治疗新靶点具有重要意义。

The production of IL-1β stimulated by Clostridium difficile toxinB in macrophages is an important cause intestinal inflammatory storms. IL-1β is the cleavage product of pro-IL-1β. However the mechanism of how toxin B could produce pro- IL-1β is still unclear. Previous results showed that toxin B promoted pro-IL-1β production by activating the p38 MAPK signaling pathway, which depended on the canonical adaptor protein MyD88. Upon the stimulation of toxin B, FZD5, a possible macrophage surface toxin B receptor, was able to bind MyD88. Therefore, we presume that toxin B may bind to the FZD5 or other receptors and recruit MyD88, which in turn activate downstream signaling pathways to promote the production of pro-IL-1β. In this project, we will firstly verify the effect of MyD88 on pro-IL-1β formation, then observe the interaction between MyD88 and the receptor by immunoprecipitation and fluorescence co-localization, define the function of the receptor through constructing the receptor gene knockout cell line, and finally elucidate the mechanism of toxin B promoting macrophage production of pro-IL-1β both in vitro and in vivo. The goal of this project is to further understand the pathogenic mechanism of C. difficile in intestinal inflammation and to find new targets for immunotherapy of C. difficile enteritis.