III型干扰素是新近发现的一类细胞因子，与I型干扰素相似，可激活细胞的抗病毒免疫功能。III型干扰素的基因多态性位点与HCV感染的自愈以及治疗转归密切相关，提示其在肝脏抗病毒免疫应答中发挥关键作用。肝细胞显示了不同于多数有核细胞的免疫反应特点，免疫激活后特异性的只产生III型干扰素而非I型干扰素，这一转录激活的调控机制并不清楚。这里，我们假设肝细胞的特殊转录因子表达谱以及I型和III型干扰素基因区域的表观遗传状态控制了III型干扰素的特异性表达。该项目将重点研究肝细胞的IRF和NF-kB家族转录因子的表达激活、干扰素启动子区域的DNA甲基化和组蛋白乙酰化修饰，进而验证各转录因子与转录调控区域的结合，及其对干扰素基因的调控作用，阐明肝细胞特异性表达III型而非I型干扰素的调控机制。这一研究对进一步了解人类肝脏的免疫规律，阐明机体抗HBV和HCV感染的免疫学机制具有重要意义。

Type III interferons (IFNs), a group of newly indentified cytokines, have similar biological functions with type I IFNs which trigger anti-viral immunity during viral infection. Recently, genome wide association studies (GWAS) indicate that type III IFNs play crucial roles in liver immunity, affecting both spontaneous recovery and therapy outcomes in HCV-infected individuals. Subsequent research reveals an interesting immunological feature of human hepatocytes that specifically produce type III IFNs and not type I IFNs, however, the underlying mechanism for this specificity is unclear. Here, we hypothesize that type III IFN expression by hepatocytes is regulated by both specific transcription factors and epigenetic status of IFN gene promoters in hepatocytes. First, we will examine the expression and regulation of several important anti-viral transcription factors, including interferon regulatory factors (IRFs) and NF-κBs family. We will then study the DNA methylation status and histone modifications in IFN promoter region. Finally, we will test the binding of transcription factors to regulatory elements in IFN promoters and confirm their functions. The results of this study will help us to understand more about liver immune responses and their anti-viral roles during HBV and HCV infection.

多种人类病原感染肝脏，肝脏区域免疫是机体保护性免疫的重要组成部分，发现III型干扰素（IFN lambda，IFNLs）与肝脏抗病毒免疫密切相关是该领域的重要进展。本课题集中于研究肝细胞免疫应答诱导产生IFNL的调控机制。发现仙台病毒（SeV）和肠道病毒71型（EV71）感染人肝癌细胞系和人原代肝细胞，可显著诱导III型干扰素分泌，而无明显I型干扰素产生。机制研究表明人肝细胞分别通过RIG-I或MDA5蛋白识别SeV或EV71感染，下游通过MAVS蛋白介导IRF1和IRF3等激活诱导IFNLs基因的表达。细胞上清中IFNs活性测试进一步明确了肝细胞免疫激活后主要产生III型而非I型IFNs。此外，不同于外周血单个核细胞，我们发现人肝组织和脾脏来源的免疫细胞组成性表达IFNL1/4而非IFNL2/3转录本。佛波酯（PMA）和大肠杆菌刺激后，肝脏免疫细胞分泌产生I型和III型干扰素，而外周血细胞仅产生I型干扰素。删除浆细胞样树突状细胞（pDC）实验表明，I型干扰素可能由pDC产生。最后，单细胞转录组学的数据提示肝、脾组织中的NK和T淋巴细胞可能是III型干扰素的主要来源。综上所述，本研究揭示了III型而非I型IFNs是肝脏区域免疫的重要特点，发现不同RIG-I样受体免疫识别的分工机制，并提示肝内NK和T淋巴细胞可能是肝内III型IFNs的另一重要来源。