髓源性抑制细胞（MDSC）在肿瘤免疫逃逸中发挥着重要作用，调控MDSC生物学功能在免疫治疗中具有重要价值，但调控机制尚不清楚。CD40在细胞凋亡、分化以及诱导Th扩增中均发挥重要作用。课题组前期工作发现胃癌微环境中MDSC表达CD40，因此推测CD40在调控胃癌微环境MDSC生物学功能中可能发挥关键作用。鉴此，本项目拟开展以下研究：（1）通过病例研究，分析CD40在胃癌患者MDSC表达的临床意义，并探讨CD40表达与MDSC功能之间的相关性；（2）利用模式动物获得CD40-和CD40+MDSC细胞，体外实验分析CD40信号调控MDSC凋亡、诱导Treg扩增以及向DC分化中的生物学功能；体内实验探讨CD40在MDSC介导的肿瘤免疫逃逸中的作用。（3）利用基因芯片技术，分析CD40激发前后MDSC功能分子变化情况，利用特异性阻滞剂进行体内外干预，分析CD40调控MDSC生物学功能的分子机制。

Myeloid-derived suppressor cells (MDSCs) are potent immune-suppressive cells promoting tumor progression and metastasis. However, the regulatory mechnism MDSC in tumor enviroment remains unclear. CD40 is an important molecule in the regulations of celluar biology including anti-apoptosis, Th subset induction, and cell differentiation of myeloid cells.In previous work,we found that CD40 expression is detectable on gastric carcinoma infiltrating MDSC at a low level. Thus, we hypotheses that CD40 play an important role in apoptosis resistance, Treg induction, and cell differentiation of MDSC in tumor microenviroment of gastric carcinoma. To confirm the above hypotheses, we intend to carry out these following experiments: (1) to study the clincal significance of CD40 expreased on MDSC in gastric carcinoma, and to analysis the association of CD40+MDSC with Treg, apoptotic index of MDSC or number of MDSC in tumor microenviroment of gastric carcinoma; (2) Using CD40 knockout and wildtype mice, to analyze the role of CD40 in regulating MDSC biological functions including treg expansion, MDSC accumulation and differentiation in vitro, and to assess the effect of CD40 on MDSC-mediated immune escape through tumor-bearing mouse model; (3) To analyze the changes of function-associated membrane molecules and signal molecules of MDSC sitmulated with CD40L; in following functional analysis, we will use special inhibitions to confirm the molecular mechanism of CD40 in regulation of MDSC. In summary, we aim to anayze the effect of CD40 on MDSC biology and advance our understanding of the tumor immune evasion mechanism, which may lead to new strategies for treatment of gastric carcinoma.