烧伤后TNF-α诱导蛋白-8样分子2介导树突状细胞免疫功能障碍与调节机制

The impaired immune function of dendritic cell (DC) is hallmark of septic syndrome, however, the precise mechanisms underlying DC dysfunction and interventional strategy remain unsolved. In our previous study, we had demonstrated that tumor necrosis factor-alpha induced protein 8 like-2 (TIPE2) was expressed in T lymphocyte and mediates T-cell proliferation. As important antigen presenting cells, the functional status of DC directly affects the differentiation and proliferation of T cells. The present study was performed to investigate whether TIPE2 was expressed in DCs, and its regulatory mechanism of TIPE2 in mediated DC cellular immune dysfunction after major burns. The main research contents of current project include various aspects as follows: (1) to investigate the effect of TIPE2 on the differentiation, maturation as well as antigen presenting ability of DCs; (2) to study exact relationship between TIPE2 and DCs mediated T lymphocyte proliferation; (3) to evaluate the relationship between TIPE2 and DC dysfunction and clinical significance in the development of postburn sepsis. Our findings will help to clarify the underlying mechanisms of TIPE2 in immune dysfunction of DCs, and develop novel immunomodulatory strategy for improving the clinical outcome of patients with severe injury and subsequent septic complications. .

树突状细胞(DC)免疫功能障碍是脓毒症发病的重要基础，但迄今为止其确切分子机制尚未阐明，临床缺乏有效的干预措施。我们前期实验发现新的负向调控蛋白——肿瘤坏死因子-α诱导蛋白-8样分子2(TIPE2)在T淋巴细胞中存在表达并介导T淋巴细胞增殖反应。DC细胞作为重要的抗原提呈细胞，其功能状态直接影响T淋巴细胞的分化和增殖，因此，本项目拟研究TIPE2在DC细胞中的表达规律，并从多个层面探讨TIPE2在烧伤后DC细胞功能障碍的作用与调控机制。主要内容包括：(1)探讨TIPE2对DC细胞分化成熟及抗原呈递能力的影响；(2)研究TIPE2与DC介导T淋巴细胞增殖反应的本质联系；(3)明确TIPE2与烧伤后DC免疫紊乱的关系及其临床意义。本课题旨在从新的角度进一步认识TIPE2介导DC细胞免疫障碍的作用与分子机制，为探索严重烧伤后脓毒症免疫调理提供新思路。

肿瘤坏死因子-α诱导蛋白-8样分子2(tumor necrosis factor-α induced protein 8 like-2, TIPE2)在机体免疫细胞内存在表达，可能参与烧伤后脓毒症的病理生理过程。但TIPE2表达是否影响树突状细胞(dendritic cells, DC)的免疫功能迄今尚不清楚。该项目重点探讨TIPE2在DC细胞中的表达规律，并从多个层面探讨TIPE2在烧伤后DC细胞功能障碍的作用与调控机制。取得的主要研究结果如下：(1) 激光共聚焦显微镜成像分析显示TIPE2在DC内存在基因和蛋白表达。(2) 流式结果显示，CD80、CD86及]MHC-II表达在TIPE2沉默DC细胞组显著增强，TIPE2过表达组3种表面分子的表达均明显降低。小鼠烫伤24 h后，siRNA-TIPE2转染组DC表面3种分子表达均较烫伤组出现显著上调，TIPE2 RNA转染组其表达则明显下调。(3) siRNA-TIPE2转染组DC细胞上清液中检测到较高水平IL-12、TNF-α。小鼠严重烫伤后，siRNA-TIPE2转染组其生成量显著升高，而TIPE2 RNA转染组两种细胞因子水平明显降低。(4) 沉默TIPE2表达后T细胞增殖活性较正常组增强。小鼠烫伤24 h后，siRNA-TIPE2转染组T细胞增殖活性明显增强，TIPE2上调组T细胞增殖活性则显著减弱。(5) TIPE2-RNA转染DC细胞后，IL-2水平及T细胞NF-AT活性显著降低。烫伤24 h后TIPE2 RNA转染组IL-2水平及T细胞NF-AT活性较烫伤组明显降低，TIPE2 siRNA转染组IL-2生成量及T细胞NF-AT活性显著升高。(6) TIPE2 siRNA转染DC细胞后，IFN-γ生成量增加，IL-4生成量下降。与烫伤组相比，TIPE2 RNA转染组IFN-γ水平降低而IL-4含量升高，TIPE2 siRNA转染组，IFN-γ水平上升而IL-4含量显著降低。上述研究进一步论证了TIPE2 是介导严重烧伤后DC 细胞免疫功能障碍的关键调控分子，并很可能通过影响DC细胞分化成熟及介导DC 细胞对T 淋巴细胞的增殖反应与分化发挥对DC 细胞的免疫调节效应。