MBL在白假丝酵母菌感染中对Th17/Treg细胞平衡调节作用及机制

Candida albicans (C.albicans), the most common human fungal pathogen in clinic, so, it is very significant to make more in-depth studies on immune response to C.albicans as the situation of fungal infections becomes increasingly serious. It has been proved that Thl7 cells and regulatory T cells (Treg) play key roles in anti-C.albicans immune responses, and cytokine secretion and toll-like receptors (TLRs) are key factors in regulating the differeatiation and balance of T Th17 cells and Treg cells. We have found that mannan-binding lectin (MBL), the key molecule in innate immunity, can not only affect the proliferation and cytokine secretion of CD4+ T cells, but also regulate the expression of TLR2 and TLR4. Based on obove, firstly we will reveal the clinical correlation between MBL concentration and the cell numbers of Th17 cells and Treg cells through analysis of C.albicans-infected blood specimen. Furthermore, we will establish C.albicans infection models in vitro and in vivo, and analyze how MBL affect the impact the differeatiation of Th17 cells and Treg cells. In addition, we will explore the related signal pathways which regulated the relation of the interaction of MBL to TLRs, and to clarify the mechanism how MBL regulates Th17/Treg balance. We would propose a new opnion that MBL can regulate TH17/Treg balance to inhibit C.albicans infection, and provide new ideas for the prevention and treatment of C.albicans infection.

真菌感染形势日益严峻，白假丝酵母菌是临床最常见病原真菌，深入研究白假丝酵母菌感染免疫意义重大。已证实Thl7细胞及调节性T细胞(Treg)在抗白假丝酵母菌感染免疫中至关重要，而细胞因子环境与Toll受体（TLRs）是调节Th17、Treg细胞分化及平衡的重要因素。我们发现"天然免疫的关键分子"-甘露聚糖结合凝集素（MBL）不仅能影响CD4+T细胞增殖和细胞因子分泌，还可调节TLR2和TLR4的表达，据此提出本项目。首先分析白假丝酵母菌感染者标本，揭示MBL浓度与Th17及Treg数量的相关性；进一步建立白假丝酵母菌感染的体外模型和动物模型，剖析MBL对Th17、Treg细胞亚型分化的影响；再引入MBL与TLRs的相互关系来探讨有关信号通路，阐明MBL调控Th17/Treg细胞平衡的机制。提出MBL通过调节Th17/Treg细胞平衡抗白假丝酵母菌感染新观点，为白假丝酵母菌感染防治提供新思路。

真菌感染形势日益严峻，白假丝酵母菌（C.albicans）是临床上最常见病原真菌，深入研究抗白假丝酵母菌感染免疫意义重大。甘露聚糖结合凝集素（MBL）是天然免疫的关键分子。. 本研究首先通过临床标本探讨MBL、Th17细胞、Treg 细胞在C.albicans 感染患者血浆中的表达变化及三者之间的相互关系。发现与健康组对比，C.albicans感染的患者血清中MBL浓度显著升高，Treg细胞比例和Th17细胞比例均增加，而且炎症性细胞因子IL-1β的表达水平显著性升高。证明在C.albicans感染中MBL表达水平与Th17细胞、Treg细胞的表达呈一定相关性。. 进一步通过建立体外研究模型和MBL基因敲除小鼠模型，分析在C.albicans感染中MBL对调节Th17/Treg细胞平衡调节作用。发现：MBL不仅能够抑制活化的CD4+T细胞增殖，而且能够以浓度依赖方式对Thl7细胞诱导分化相关细胞因子（IL-17、IL-21）及Treg细胞诱导分化相关细胞因子（IL-2、IL-10）的表达均具有调节作用；MBL还能够直接抑制初始CD4+T细胞向Th17细胞诱导分化，增强人初始CD4+T细胞向Treg细胞诱导分化，用MBL基因敲除小鼠模型，我们得到类似实验结果。在C. albicans感染的体外实验和动物实验中我们则发现，MBL对Th17细胞亚型分化及核因子RORc的表达具有显著的抑制作用，而对Treg细胞诱导分化及Foxp3的表达不具有调节作用。上述实验结果提示，MBL具有调节Th17、Treg细胞亚型分化的功能，但是在C.albicans感染中，MBL主要通过抑制Th17细胞诱导分化来实现调控Th17/Treg细胞免疫平衡的。. 最后我们用上述研究模型，分析了MBL对Th17/Treg细胞平衡调节机制。结果显示，MBL不仅能够抑制P-JAK2、P-STAT3蛋白表达，增强P-JAK3、P-STAT5的表达；而且能够抑制TLR2、TLR4的表达及p65/ NF-κB由胞浆向胞核转位；MBL还能够抑制Syk、ERK及p38的磷酸化。提示MBL通过JAK/STAT、TLR- NF-κB、dectin-1介导Syk/CARD9信号途径调节Th17/Treg细胞平衡。. 该研究为C.albicans感染的防治提供新的理论依据和新的靶点，具有潜在的医学实践意义。