转录因子Fox P3与调节性T细胞的表达调控在播散性毛孢子菌病发病中的作用

Trichosporon asahii (T. asahii) is a major pathogen causing trichosporosis. In 2000, we reported the first case of disseminated trichosporonosis in China. In recent years, with the wide application of cytotoxic drugs in chemotherapy, corticosteroid and organ transplantation and the increase of malignancies, the incidence of disseminated trichosporonosis is also increasing in recent years. Previous studies reported trichosprosis was mainly found in patients with hematological disease, tumor, AIDS, etc, and less found in healthy subjects. This suggests that immune function plays an important role in defense against fungal infection. However, the reasons that the immune system of host cannot promptly clear the pathogens following T. asahii infection are still unclear. Regulatory T cells (Tregs) are important subpopulation of T lymphocyte in immune system.Foxp3 is the only marker of Treg, which seems to act as a "master switch" for the development and function of Treg. Mice and human lacking functional expression of Foxp3 completely lack Treg and develop severe autoimmunity. Moreover, ectopic expression of Foxp3 in conventional T cells endows them with the part or all phenotype and function of Treg. Until recently, Foxp3 expression has been thought to be restricted to the T-cell lineage. This project intends to establish a mouse model of disseminated Trichosporon infection after FoxP3, studies in various organs and regulatory T cells in the expression and regulation mode, analysis of the FoxP3 gene silencing or in vivo expression of murine infection, NF kappa B activation and NF kappa B regulation of cytokine IL-4 expression, IL-10 effects of level, Foxp3 clarify role of transcriptional regulation in pathogenesis of disseminated Trichosporon.

阿萨希毛孢子菌(T.asahii)是播散性毛孢子菌病的主要病原菌，可导致系统性、致命性感染，T.asahii进入宿主体内后是否致病，是由宿主的免疫防御状态和菌株致病力两个因素决定的。调节性T 细胞是一类可调节其他免疫细胞的增殖、分化与功能，维持机体免疫平衡状态的T 淋巴细胞。在人及小鼠中，转录因子FoxP3 在调节性T 细胞的发育、分化及免疫调节功能的发挥中起重要作用，可作为调节性T 细胞的分子标记。本项目拟建立小鼠播散性毛孢子菌模型，研究感染后FoxP3 在各脏器及调节性T细胞中的表达及调控模式，分析FoxP3 基因沉默或体内过表达情况下对小鼠感染、NF-κB 激活及NF-κB 所调控的细胞因子IL-4、IL-10 表达水平的影响，阐明Foxp3 的转录调控作用在播散性毛孢子菌发病中作用。

阿萨希毛孢子菌(Trichosporon asahii,T.asahii)是播散性毛孢子菌病的主要病原菌，可导致系统性、致命性感染。近年来，随着激素和免疫抑制剂的应用，以及肿瘤、血液病、艾滋病的增多，该病发病率逐年上升。研究表明，T. asahii进入宿主体内后是否致病，是由宿主的免疫防御状态和菌株致病力两个因素决定的。本课题组近3年来围绕调节性T 细胞（T regulatory cells, Treg）、转录因子Foxp3及单核源的树突状细胞在播撒性毛孢子菌病中作用展开了系列研究。我们通过建立小鼠播散性毛孢子菌病模型，研究感染后Foxp3 在各脏器及调节性T细胞中的表达、Foxp3调控的细胞因子白介素10（IL-10）、转化生长因子β1（TGF-β1）的表达水平，结果发现播散性阿萨希毛孢子菌感染小鼠后可以诱导CD4+CD25+Foxp3+调节性T细胞及其细胞因子IL-10、TGF-β1表达增高，调节性T细胞及细胞因子IL-10、TGF-β1参与播散性毛孢子菌感染的免疫应答反应；调节性T细胞与小鼠血清IL-10和TGF-β1浓度及脾脏组织中IL-10 mRNA、TGF-β1 mRNA表达水平呈明显正相关，提示调节性T细胞可能通过分泌抑制性细胞因子IL-10、TGF-β1发挥免疫调节作用；调节性T细胞及细胞因子IL-10、TGF-β1可能减弱了机体清除阿萨希毛孢子菌的能力，为阿萨希毛孢子菌的存活提供了有利条件。我们还通过体外诱导培养正常人外周血单核源树突状细胞（dendritic cells，DCs），并与不同浓度的体外热灭活阿萨希毛孢子菌孢子培养，研究热灭活阿萨希毛孢子菌孢子对健康人外周血DCs表型及功能的影响，探讨DCs在T.asahii感染中可能发挥的作用。结果发现诱导孵育过程中，DCs形态发生明显改变；24h时部分DCs内可观察到不止一个被吞噬的T.asahii孢子，DCs表面共刺激分子（CD80、CD86、CD83）、促进T淋巴细胞增殖的能力和分泌IL-10及IL-12能力均明显升高。说明人外周血DCs吞噬热灭活的T.asahii孢子后，形态发生改变，表面分子表达水平升高，DCs进一步成熟与活化，启动宿主的有效免疫应答，从而促进了宿主对阿萨希毛孢子菌的清除。综上，我们围绕调节性T 细胞（T regulatory cells，Treg）、转录因子Foxp3及