促供者T细胞二级淋巴器官滞留诱导移植后免疫耐受的机制研究

T cells immune tolerance is an important mechanism that attenuates acute graft versus host disease (aGVHD) post allogeneic stem cell transplantation (HSCT). T cells immune tolerance can be categorized into anergy, exhaustion, or senescence depending on its immune response states. Secondary lymphoid organs (SLO) are critical for the induction of immune tolerance. Our previous study showed that combined CCR5 and CXCR3 blockade could retain donor-derived lymphocytes within SLO and attenuate murine aGVHD. But the potential mechanisms remain uncertain. Based on our previous study, we hypothesized that combined CCR5 and CXCR3 blockade could induce T cells anergy, exhaustion, or senescence in SLO by downregulation of pro-inflammation cytokine secretion and upregulation of inhibitory moleculars on T cells. In order to verify the hypothesis, we will test T cell immune response according to the mixed lymphocyte response (MLR) in vitro. In vivo, we will detect T cells function, including anergy, exhaustion and senescence in the MHC-mismatched aGVHD murine models and secondary adoptive murine models. This study will provide a new mechanism of the immunopathophysiology of aGVHD, which may potentially help to develop a new strategy for preventing aGVHD.

T细胞免疫耐受是减轻急性移植物抗宿主病（aGVHD）的重要机制。根据其功能状态，T细胞免疫耐受可分为无能、耗竭及衰老。而二级淋巴器官（SLO）是诱导T细胞免疫耐受发生的重要场所。我们前期研究发现靶向阻断CCR5及CXCR3可促进T细胞SLO滞留减轻aGVHD，但其机制不清。因此，本课题提出以下设想：联合阻断CCR5及CXCR3可通过下调炎症因子分泌水平，上调T细胞抑制性分子表达，促进无能、耗竭及衰老等免疫现象的发生，参与改善aGVHD。本课题基于前期实验基础，拟通过体外混合淋巴细胞反应、体内aGVHD模型及二次移植模型，研究促T细胞滞留SLO后免疫耐受的功能状态，揭示aGVHD的免疫耐受调控新机制，为aGVHD的防治提供新的靶点和方向。

急性移植物抗宿主病(acute graft-versus-host disease, aGVHD)是异基因造血干细胞移植(allo-HSCT)后最主要的并发症，常规免疫抑制剂治疗常因明显的不良反应而应用受限。我们前期研究发现联合靶向阻断趋化因子受体CCR5和CXCR3(以下简称联合阻断组)能够明显延长aGVHD小鼠生存，抑制T细胞功能，呈现免疫耐受的状态。树突状细胞(DC)作为最有效的抗原递呈细胞(APC)，在aGVHD中对T细胞的活化及功能调节发挥重要作用。因此，本研究在联合靶向阻断CCR5和CXCR3改善小鼠aGVHD模型的基础上，研究DC的变化及其在诱导移植免疫耐受中的作用。在小鼠模型中，与GVHD组相比，联合阻断组脾脏中DC数量增加，凋亡减少，共刺激分子CD86下调，而PD-L1和PD-L2表达均明显上调，并且通过药物特异阻断T细胞PD-1受体与DC上PD-L1/2结合可逆转联合阻断组脾脏DC对MLR中T细胞的增殖和活化作用。本研究表明在CCR5及CXCR3联合阻断的条件下，DC表面PD-L1/L2的上调可能是诱导T细胞免疫耐受的一大重要机制，为诱导异基因造血干细胞移植后诱导免疫耐受提供了良好模型，为aGVHD的预防提供了新的思路。