Plasmacytoid Dendritic Cells and Their Role in Transplant Tolerance

描述(申请人提供)：同种异体肝移植耐受性良好，与肝脏同时移植的其他实体器官移植，如小肠和肾脏，移植效果较好。然而，“肝耐受”的机制尚未阐明。已有研究表明，与淋巴组织相比，肝脏树突状细胞(DC)具有免疫调节功能，抗原提呈功能和免疫刺激功能减弱。最近的焦点是DC亚群之间存在功能差异，包括浆细胞样树突状细胞和髓样细胞样树突状细胞。有人假设，不成熟的PDC具有天生的耐受性。事实上，来自多项研究的数据表明，PDC在耐受性的产生中发挥着独特而重要的作用。当PDC暴露在肝脏独特的免疫抑制微环境中时，其耐受性可能会进一步增强，产生免疫调节性肝树突状细胞(HDC)，从而削弱(同种异体反应)T细胞的诱导。事实上，最近一篇研究排斥小肠移植的患者的MDC与PDC的比率较高，支持PDC的耐受作用(4)。目前对DC在小肠移植中的作用知之甚少。本工作拟研究肝和小肠PDC的特性，以阐明PDC诱导耐受的机制。利用流式细胞术、逆转录聚合酶链式反应、酶联免疫吸附试验、混合白细胞反应和T细胞抑制试验，我们的目的是阐明肝脏PDC诱导耐受的机制，无论是通过T细胞凋亡和/或T调节细胞的产生。我们将进一步研究单独的小肠移植如何改变免疫调节特性。在我们的最终目标中，我们将利用肝脏PDC作为细胞疗法，在一种新的小鼠小肠移植模型中诱导抗原特异性耐受。执行拟议研究的模型和技术目前已在赞助商的实验室中到位，从而使拟议的目标立即可行。肝PDC在移植模型中具有诱导抗原特异性耐受的潜能。通过利用抗原特异性细胞疗法，我们有可能改变器官移植的结果和管理。 公共卫生相关性：肝脏移植耐受性良好，与肝脏同时移植的其他实体器官移植，如小肠和肾脏，显示出更好的移植结果。特定的免疫细胞被认为具有诱导耐受的能力。在移植患者中诱导耐受的能力可以显著改善移植排斥反应、存活率和患者的生活质量。

DESCRIPTION (provided by applicant): Liver allografts are well tolerated, and other solid organ allografts, such as the small intestine and kidney, transplanted concurrently with livers show improved graft outcomes. However, the mechanisms underlying "hepatic tolerance" have yet to be elucidated. Previous data show that liver dendritic cells (DC) can regulate immune responses and have diminished antigen (Ag) presenting and immune stimulatory function compared with those in lymphoid tissue. Recent focus to explain this has been that functional differences between DC subsets including plasmacytoid (p)DC and myeloid (m)DC exist. It has been hypothesized that immature pDC are inherently tolerogenic. Indeed, data from multiple studies show that pDC play a unique and important role in the generation of tolerance. The tolerogenicity of pDC may be further enhanced when exposed to the unique immunosuppressive microenvironment of the liver, generating immunoregulatory hepatic DC (HDC) that impair induction of (alloreactive) T cells (3). Indeed, a recent paper examining patients who are rejecting small intestine transplant have a higher ratio of mDC to pDC, supporting a tolerogenic role for pDC (4). Little is currently known about the role of DC in small intestine transplant. This work proposes to investigate properties of hepatic and small intestine pDC to elucidate a mechanism by which pDC induce tolerance. Utilizing flow cytometry, reverse transcriptase polymerase chain reaction, enzyme-linked immunosorbent assay, mixed leukocyte reaction and T cell suppression assays, we propose in our Aims to elucidate a mechanism by which hepatic pDC induce tolerance, whether by T cell apoptosis and/or the generation of T regulatory cells. We will further examine how small intestinal transplantation alone alters immune regulatory properties. In our final Aim, we will utilize hepatic pDC as cellular therapy in a novel murine model of small intestine transplant to induce Ag specific tolerance. The models and techniques to perform the proposed studies are currently in place in the sponsor's laboratory, making the proposed Aims immediately feasible. Hepatic pDC have the potential to induce Ag specific tolerance in transplant models. By utilizing antigen specific cellular therapy, we have the potential to transform the outcome and management of organ transplantation. PUBLIC HEALTH RELEVANCE: Liver transplants are well tolerated, and other solid organ transplants, such as the small intestine and kidneys, transplanted concurrently with livers show improved graft outcomes. Specific immune cells have been implicated in the ability to induce tolerance. The ability to induce tolerance in transplant patients could significantly improve graft rejection, survival, and patient quality of life outcome.