CD11c表达对抗原递呈细胞功能和急性移植物抗宿主病的影响

Acute graft versus host disease (aGVHD) is one of major complications of allogeneic hematopoietic stem cell transplantation (allo-HSCT). aGVHD is initiated by host antigen-presenting cells (APCs), which prime alloreactive donor T cells, causing donor T cell activation in allograft and therefore inducing aGVHD. Even with pharmacologic immunosuppression, aGVHD remains a major cause of morbidity and mortality of allo-HSCT. Therefore, it is necessary to define new targets and develop novel therapeutic strategies accordingly to treat or prevent aGVHD. CD11c is an adhesion molecule belonging to beta2 integrin. Unlike other beta2 integrins such as CD11a and CD11b, CD11c is specifically (in mice) or highly (in humans) expressed on DCs, the most potent APCs. However, its function in APC-T cell interactions has not been well studied. Our recent research indicated that ablation of CD11c on APCs in mice decreased T cell activation in inflammatory tissues, possibly by affecting APC functions, indicating a crucial role of CD11c in APC priming of T cell activation. However, the role of CD11c in aGVHD remains unknown..In our current application, we will employ mice with genetic ablation of CD11c and systematically examine changes in gene expression, functions and interaction with T cells of APCs deficient in CD11c. We will also use in vivo mouse transplantation model to examine how CD11c affect aGVHD. In addition, clinical specimens will be used to explore the changes in CD11c levels on APCs during the treatment of aGVHD and examine the influence of CD11c on APC functions and subsequently on T cell activation. Our approach will reveal a potential role of CD11c in APC functions with subsequent effects on T cell activation and its contribution to aGVHD. Therefore, our application will provide a potential new target and help develop novel therapeutic strategies for treatment and prevention of aGVHD.

急性移植物抗宿主病（aGVHD）是异基因造血干细胞移植的主要并发症，宿主抗原递呈细胞（APC）与供者T细胞相互作用，从而激活T细胞是诱导aGVHD的必要条件。CD11c高表达于树突状细胞等APC，但对于其在APC激活T细胞过程中的作用尚无报导。我们的研究显示，CD11c表达缺陷将导致炎症环境下T细胞反应性下降，且可能与APC的功能下降有关，提示CD11c在APC与T细胞相互作用中发挥重要作用。但对其影响APC功能的确切机制以及是否可以影响aGVHD的发生并不清楚。本研究中我们将首先利用CD11c基因敲除小鼠研究敲除CD11c后APC基因表达、功能以及与T细胞相互作用的变化，同时利用GVHD动物模型研究减少APC的CD11c表达对aGVHD的影响。此外，还将利用临床标本探讨CD11c在aGVHD治疗中的变化以及对APC功能的影响。本研究结果将为aGVHD的治疗提供新策略。

CD11c作为β2整合素家族的一员，是树突状细胞（DCs）的表面标志。急性移植物抗宿主病（aGVHD）是异基因造血干细胞移植（allo-HSCT）后严重威胁生命的并发症之一。因此，深入了解aGVHD的发生和致病机制具有重要意义。目前的研究认为，aGVHD由宿主抗原提呈细胞（APCs）引起同种反应性T细胞扩增和成熟而启动。CD11c分子如何维持DCs的功能，以及DCs上的CD11c分子是否参与aGVHD的发病机制还有待探究。我们通过在体外试验中阻断人外周血单核细胞来源DCs（MoDCs）上的CD11c分子研究CD11c在活化同种异基因T淋巴细胞中的功能。利用Itgax基因敲除小鼠，建立MHC不匹配allo-BMT模型，分别研究CD11c分子在供鼠和受鼠在aGVHD发病时的作用。我们通过体外功能实验研究CD11c缺陷DCs的抗原递呈功能和趋化功能。在机制研究中，我们以内源性CD11c为靶点，在DC 2.4细胞系中获取与CD11c直接作用的蛋白，通过质谱分析得到相关性最高的分子，并通过免疫共沉淀（Co-IP）和Western Blot进行验证。体外共培养实验中，阻断人MoDCs上的CD11c分子减少了同种异基因CD4+ T细胞的增殖和表达IFN-γ的辅助性T淋巴细胞1（Th1）的分化。在小鼠allo-BMT模型中，由于移植后早期CD11c-/-受鼠体内的同种反应性CD4+ T细胞增殖减少和aGVHD靶器官中表达IFN-γ的CD4+ Th 1细胞和CD8+ T细胞减少，CD11c-/-受鼠发生aGVHD的症状减轻，总体生存时间延长。然而，回输CD11c缺陷的供者骨髓（BM）细胞可以导致allo-BMT后供者BM细胞归巢和重建失败。机制研究表明CD11c分子通过Hsp 90-MHC II途径促进DCs的抗原提呈功能，通过磷酸化Akt和Erk 1/2维持DCs的活化和趋化功能。