Research On The Immunosuppression Effects And Mechanism Of Regulatory T Cells From Gastric Cancer On Dendritic Cells

Objective: Dendritic cells (DCs), due to its potent immune stimulating function, was termed as 'professional antigen presenting cells' and play important role in anti-cancer response in immune system. DCs possess brilliant future in clinical anti-cancer immunotherapy. But under the circumstances of malignant tumor, DCs usually show immature of semi-mature states, and its function was suppressed. This phenomenon had relationship with regulatory T cell (Treg). However, this mechanism remains unclear. In this research the Treg expression, distinguishing features and its function in DCs immunosuppression were investigated in gastric cancer in order to explore the mechanisms of Treg immunosuppression.Methods: 1. Freezing sections with fluorescent antibodies with flowcytometry were used to illustrate Treg and DCs expressions in peripheral blood, gastric cancer tissue and para-tumor lymph nodes comparing with that in control. The relationship of Treg expression to gastric cancer pathological features was analyzed. 2. MACS method was applied to purify Treg from peripheral blood and para-tumor lymph nodes. The purity, apoptosis rate and distinct gene expression of Foxp3 and cytokines of Treg from both sources were compared. Treg's activating method was also analyzed. 3. In order to investigate the effects and mechanism of Treg immunosuppression, DCs treated with Treg from gastric cancer under different ratio and various time were analyzed by detecting the immunophenotype, cytokines secretion, T lymphocyte stimulation ability. IL-10 interposing and apoptosis inducing were also analyzed to explain the mechanism of Treg immunosuppression.Results: 1. Treg levels within peripheral blood, tumor tissue and para-tumor lymph nodes of gastric cancer were significantly arisen comparing with control. Treg expression was correlated with lymph node metastasis and TNM classification of gastric cancer. The level of Treg is higher in positive lymph node metatasis and late TNM classification. S100positive DCs expressions and DCs phenotype arisen from peripheral blood were significantly lower in gastric cancer, and also correlated with TNM classification of gastric cancer. 2. Large amount of Treg with high purity could be separated from peripheral blood and lymph node of gastric cancer by MASC methods. The peripheral blood source yields more Treg with less apoptosis rate and would be better source for Treg separation. Treg has distinct Foxp3 and suppressing cytokines gene expression, which imply its immunosuppression function in vivo. 3. Treg from gastric cancer show time and dose depending significant suppressing effects on DCs immunity. The effects were demonstrated by detecting the phenotype, IL-12 secretion and lymphocyte stimulation. And the mechanism of Treg immunosuppression effects were analyzed on IL-10 interposing and inducing of apoptosis.Conclusion: Treg expression in gastric cancer is upregulated and may suppress DCs immunity by apoptosis inducing and IL-10 interposing.