神经母细胞瘤（NB）的免疫治疗已为人们所关注和研究，但存在肿瘤微环境导致免疫细胞受抑制的问题。γδT细胞在NB免疫治疗中具有巨大潜力，我们前期研究提示活化性受体DNAM-1发挥重要的抗肿瘤作用，NBγδT细胞中DNAM-1表达下调，肿瘤杀伤减弱；深入研究发现肿瘤浸润及骨髓转移患者的骨髓γδT细胞中DNAM-1表达进一步下调，体外与NB细胞共培养可下调γδT细胞中DNAM-1的表达，下调程度与肿瘤CD112的表达正相关。基于NBγδT细胞中DNAM-1表达下调和功能减弱的问题，我们提出假说：CD112通过抑制性受体CD112R负调控NBγδT细胞中DNAM-1的表达，抑制γδT细胞的抗肿瘤作用。本研究旨在利用慢病毒过表达/敲减、共培养、中和抗体、动物模型等方法研究NBγδT细胞中DNAM-1表达和功能的负调控机制，探索如何改善其免疫抑制状态，为γδT细胞用于NB临床治疗提供理论支持。

Immunotherapy for neuroblastoma (NB) has gradually attracted people's attention, but the suppression of immune cells led by tumor microenvironment is still a serious problem. γδT cells have great potential in NB immunotherapy and the activating receptor DNAM-1 expressed on γδT cells could trigger the cytotoxic activity of immune cells and exert important anti-tumor effects. However, our previous study has revealed the poor cytotoxicty of NB γδT cells against NB cells, accompanied with down-regulation of DNAM-1. Our preliminary research found that compared with γδT cells in peripheral blood, orthotopic NB tumor infiltrating γδT cells and γδT cells in bone marrow with tumor metastasis showed further DNAM-1 reduction. Furthermore, DNAM-1 expression decreased markedly on γδT cells during the co-culture with NB cells in vitro accompanied with complicated interaction and cross-talk. The reduction of DNAM-1 expression also showed a positive correlation with CD112 expression of tumor cells in the co-culture. Based on the reduction of DNAM-1 expression and poor cytotoxicty of NB γδT cells, we hypothesize that inhibitory CD112/CD112R axis induces the down-regulation of DNAM-1 expression on NB γδT cells, thus inhibiting the anti-tumor activity of γδT cells. The aim of this study is to investigate the negative regulatory mechanism of DNAM-1 expression and γδT-cell cytotoxicity against neuroblastoma and explore the way to improve anti-tumor effects of γδT cells using lentivirus over-expression or know-down system, co-culture system, treatment of neutralizing antibodies and mouse NB tumor models. Results from this study will provide theoretical support and novel therapeutic targets for immunotherapy against NB using γδT cells.