Treg在急性GVHD小鼠体内可塑性与急性GVHD和GVL关系及机理研究

Graft-versus-host disease (GVHD) is a major complication and cause of death after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Previous studies have demonstrated that Regulatory T cells(Treg) might be utilized to prevent and treat GVHD without compromising graft-versus-leukemia (GVL). Recently, there have been increasing reports that challenge this view by demonstrating that Treg retain developmental plasticity and engineered Treg in vitro might be more plastic than natural Treg. The plasticity of Treg depends on the local internal environment. GVHD is a complex pathological process involving active immune cells and inflammatory factors/cytokines with tissue specificity and diversity. To explore the plasticity of Treg and its effects on GVHD as well as GVL, acute GVHD model of normal/leukemic mice were constructed and Treg were labelled with green fluorescent protein(GFP).The studies include following:(ⅰ) exploring the plasticity of engineered/natural Treg and the difference of plasticity in various target organs of acute GVHD; (ⅱ) studying the effects of Treg plasticity on the occurrence and development of GVHD as well as GVL; (ⅲ)studying the immune cells, inflammatory factors/cytokines and the expression of cytokine/chemokine receptors in target organs of acute GVHD. These studies will bring to light the mechanisms of the plasticity of Treg and the organ specificity and the effectors diversity of acute GVHD, and supply theoretical basis for Treg in preventing and treating GVHD.

GVHD是 allo-HSCT后主要并发症和死亡原因，我们和国外前期研究表明Treg可防治GVHD而不影响GVL。但新近对Treg可塑性的认识、尤其是体外工程化Treg比天然Treg更具有可塑性，这使Treg防治GVHD受到挑战。本研究基于Treg可塑性依赖局部内环境；GVHD是由免疫细胞与炎性/细胞因子参与的病理过程、有组织器官特异性与差异性。利用正常/白血病急性GVHD 小鼠及体外GFP 标记Treg，研究工程化和天然Treg在GVHD各组织器官的可塑性和向Th效应细胞转化的差异性；Treg可塑性对GVHD发生与发展及GVL的影响；Treg可塑性与GVHD靶组织器官的局部内环境包括：炎性/细胞因子、免疫细胞和靶组织细胞表面细胞/趋化因子受体表达的关系等。揭示Treg在各GVHD靶组织可塑性及GVHD效应因子致靶组织器官特异性与差异性机理，为临床GVHD防治提供理论依据。

GVHD是 allo-HSCT后主要并发症和死亡原因，研究表明Treg可防治GVHD而不影响GVL。但随着新近对Treg可塑性的认识，尤其是体外工程化Treg比天然Treg（nTreg）更具有可塑性，这使Treg防治GVHD受到挑战。本研究基于Treg可塑性依赖局部内环境，利用正常小鼠、移植后急性GVHD 和白血病急性GVHD 小鼠模型，研究工程化和天然Treg对GVHD发生与发展及GVL的影响，及Treg在GVHD各组织器官的可塑性差异及可塑性机理。研究结果显示，新鲜分离的nTreg作为预防性输注能有效降低aGVHD的发生率和严重程度，并且不影响GVL效应；经体外诱导的诱导性Treg（iTreg）对aGVHD的发生和严重程度无明显预防作用；经体外扩增的nTreg对于aGVHD的预防作用优于iTreg，但较新鲜分离的nTreg差；三种来源的Treg细胞在GVHD发生后输注均无明显治疗作用。三种来源的Treg细胞在GVHD环境下，均有一定程度的可塑性，可塑性程度依次为：新鲜分离的nTreg>经体外扩增的nTreg>经体外诱导的iTreg。进一步探讨Treg在GVHD环境下可塑性机理发现，Treg特异性去甲基化区域（TSDR）去甲基化水平依次为：新鲜分离的nTreg >经体外扩增的nTreg>体外诱导的iTreg，并且均在GVHD环境下降低，考虑不同来源的Treg细胞TSDR去甲基化水平差异影响其在GVHD环境下可塑性发生。本研究明确了不同来源的Treg细胞在aGVHD组织器官中可塑性程度及差异，为临床应用Treg细胞防治GVHD提供理论基础，丰富了Treg细胞在GVHD病理情况下发生可塑的机理。