黏膜相关恒定T细胞调控造血干细胞移植后肠道移植物抗宿主病发生的机制研究

As a major complication after hematopoietic stem cell transplantation (HSCT), intestinal acute graft-versus-host disease (aGVHD) post transplantation seriously affects the long-term survival of patients.Recent studies have confirmed that the homeostasis of intestinal microbial flora participates in the immune regulation of host,which is closely related to the occurrence of intestinal GVHD. Mucosal-associated invariant T cells (MAIT) is a group of innate immune cells that can affect host immune function by interacting with the intestinal flora. Based on the previous study of our team which demonstrated the correlation between early CD8+CD161hi T cell subsets (which constiute the main part of MAIT cells) and acute intestinal GVHD after transplantation, a scientific hypothesis was proposed: the number of MAIT cells infused into the host, the reconstitution of MAIT after transplantation and the intestinal flora were closely related to the occurrence of acute intestinal GVHD. MAIT may affect the occurrence of acute intestinal GVHD by recruiting to the intestinal tract and regulating microbial flora in target organs.Furthermore,they might play an immunomodulatory role on conventional T cells. This project intends to further clarify and confirm the role of interaction between MAIT cells and intestinal flora in the pathogenesis of acute intestinal GVHD after transplantation by use of in vitro functional experiments, transplantation animal model and clinical cohort. It would be possible to provide a new clinical prevention and treatment strategy for acute intestinal GVHD and improve the efficacy of transplantation.

造血干细胞移植后严重的急性肠道移植物抗宿主病(GVHD)是影响预后的重要合并症。近期研究证实肠道微生物菌群稳态参与宿主免疫调节，与肠道GVHD发生密切相关。黏膜相关恒定T细胞（mucosal-associated invariant T cell，MAIT）是一群固有免疫细胞，可改变肠道菌群影响宿主免疫功能。课题组基于前期CD8+CD161hiT细胞亚群（MAIT细胞主体）与移植后肠道急性GVHD相关性的研究，提出科学假说：移植输注的MAIT数量与移植后MAIT重建、肠道菌群及肠道急性GVHD的发生密切相关；MAIT可能通过募集在肠道靶器官中调节微生物菌群来影响GVHD发病，并可能对T细胞具有免疫调节作用。本项目拟通过体外功能试验、移植动物模型以及临床队列来阐明和证实MAIT细胞与肠道菌群的相互调节作用在移植后肠道急性GVHD发病中的角色，将有可能为肠道急性GVHD提供新的临床防治策略。

肠道急性移植物抗宿主病 （aGVHD） 是同种异体造血干细胞移植 （allo-HSCT） 后的一种严重并发症，死亡率高。粘膜相关恒定T（MAIT）细胞是一组富含肠道的先天样T细胞，可以被来自各种微生物的核黄素代谢物激活。然而，人们对MAIT细胞在人类肠道aGVHD发生中的作用或作用机制知之甚少。本项目使用多参数流式细胞术（FCM）来评估MAIT细胞的数量和功能性细胞因子。采用16S V34区扩增子测序分析移植患者肠道菌群。体外刺激和共培养测定用于研究MAIT细胞的活化和功能。采用免疫荧光技术分析MAIT细胞在肠道组织中的数量和分布。结果表明肠道aGVHD患者输注移植物中MAIT细胞的数量和比例低于无肠aGVHD患者。在输注移植物中MAIT比例高的受者在移植后早期（+14天）的肠道菌群丰度较高。当肠道aGVHD发生时，MAIT17的比例高于MAIT1。肠道aGVHD患者中具有非核黄素代谢途径的肠道菌群丰度趋于增加。MAIT细胞在白细胞介素（IL）-12/IL-18刺激（非TCR信号）下分泌更多的颗粒酶B、肿瘤坏死因子（TNF）-α和干扰素（IFN）-γ，并在CD3/CD28刺激（TCR信号）下分泌了大部分IL-17。MAIT细胞在体外抑制CD4 + T细胞的增殖。综上所述，输注移植物中MAIT细胞数量较少与肠道aGVHD发病率较高有关，移植物中MAIT细胞数量可能影响移植后早期受者肠道菌群的组成。核黄素代谢途径的菌群激活MAIT细胞并促进肠道保护因子的表达，从而影响人类肠道aGVHD的发生。该项目研究结果将有可能为急性GVHD提供新的临床防治策略，包括MAIT细胞治疗或菌群移植等，最终进一步改善移植疗效。