Plasmacytoid Dendritic Cells and Their Role in Transplant Tolerance

描述（由申请人提供）：肝脏同种异体移植物耐受性良好，与肝脏同时移植的其他实体器官同种异体移植物（如小肠和肾脏）显示出改善的移植结局。然而，“肝耐受”的机制尚未阐明。以往的研究表明，肝脏树突状细胞（DC）具有免疫调节功能，与淋巴组织相比，其抗原提呈和免疫刺激功能减弱。最近的焦点是解释这一点，DC亚群之间存在功能差异，包括浆细胞样（p）DC和髓样（m）DC。已经假设不成熟的pDC是固有的致耐受性的。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独特且重要的作用。当暴露于肝脏独特的免疫抑制微环境时，pDC的致耐受性可能进一步增强，产生免疫调节性肝DC（HDC），其损害（同种异体反应性）T细胞的诱导（3）。事实上，最近的一篇论文检查了小肠移植排斥患者的mDC与pDC的比例较高，支持pDC的致耐受性作用（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的性质，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pDC作为小肠移植的新型小鼠模型中的细胞治疗以诱导Ag特异性耐受。执行拟定研究的模型和技术目前已在申办方实验室中到位，使拟定目标立即可行。肝pDC具有在移植模型中诱导Ag特异性耐受的潜力。通过利用抗原特异性细胞治疗，我们有可能改变器官移植的结果和管理。

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.