T cell regulation by IDO-competent plasmacytoid dendritic cells

描述(由申请人提供)：炎症刺激适应性免疫的范例已经确立。矛盾的是，越来越多的证据表明，某些形式的炎症会造成局部抑制，特别是在因持续感染和肿瘤发展而遭受慢性炎症的组织中。抑制炎症可能通过抑制T细胞对肿瘤和病原体抗原的反应来促进肿瘤进展和促进免疫功能个体的病原体持久性，这些T细胞在这些组织和相关的引流淋巴结中遇到。然而，在炎症组织中产生和维持局部抑制的潜在机制还没有很好地确定。阐明促进炎症组织局部抑制的机制将为改进治疗操作提供关键的新见解和机会，通过在增强免疫抑制活性的同时引入供体(ALL)和自身(Auto)抗原来治疗高免疫综合征，如移植排斥反应、自身免疫和过敏性疾病。在之前的工作中，我们在人类和小鼠中鉴定了罕见的浆细胞样树突状细胞(PDC)群体，它们唯一能够表达免疫抑制酶吲哚-2，3-双加氧酶(IDO)。在小鼠中，I型干扰素(IFN1)是B7结扎后脾IDO活性pDC特有的上游IDO诱导剂。然而，pDC产生IFN1依赖于IDO活性，这表明IDO通过细胞自主的IFN1依赖途径放大了自己在IDO能力的pDC中的表达。与脾脏不同的是，与黑色素瘤生长相关的引流淋巴结(DLN)中的PDCs结构性地表达IDO，显示出强大的抑制活性，并激活了CD4+CD25+调节性T细胞(Treg)。我们假设，具有IDO能力的pDC产生局部抑制的能力严重依赖于pDC和Tregs之间的协同作用，这些作用放大了IDO的表达，从而在两种类型的细胞中都触发了抑制活性。在初步研究中，我们发现，用促炎剂和肿瘤促进剂佛波酯(PMA)局部治疗小鼠，通过激活PDCs表达IDO，进而通过IDO激活Tregs，从而在皮肤DLN中产生强烈的局部抑制。本研究旨在阐明PMA诱导DLN pDC表达IDO(Aim 1)，并通过IDO激活Treg旁观者抑制因子(Aim 2)的机制。产生的新知识将用于指导和评估在免疫、皮肤移植和I型自身免疫性糖尿病进展期间增强局部IDO表达的创新方法，以分别阻断T细胞对同种异体皮肤移植物和胰岛细胞的破坏。公共卫生相关性研究建议将重点放在树突状细胞的一小部分上，当树突状细胞从组织微环境接收到特定信号时，这些树突状细胞会完全抑制炎症组织中T细胞对抗原的反应。为了创造抑制的组织微环境，树突状细胞必须通过特定的信号通路与一小部分调节性T细胞相互作用。最近，我们发现，在肿瘤进展的小鼠模型中，用一种常用的促炎剂“涂抹”引起的皮肤炎症，在皮肤引流淋巴结中诱导了由树突状细胞介导的强大的抑制活性。这一观察结果为用供体同种异体移植物和自身抗原治疗小鼠以诱导耐受提供了理论基础，从而保护皮肤移植物和胰岛细胞免受T细胞介导的破坏。1

DESCRIPTION (provided by applicant): The paradigm that inflammation stimulates adaptive immunity is well established. Paradoxically, mounting evidence reveals that some forms of inflammation create local suppression, particularly in tissues subjected to chronic inflammation caused by persistent infections and developing tumors. Suppressive inflammation may facilitate tumor progression and promote pathogen persistence in immunocompetent individuals by inhibiting T cell responses to tumor and pathogen antigens encountered in these tissues and in associated draining lymph nodes. However, the underlying mechanisms that create and maintain local suppression in inflamed tissues are not well defined. Elucidating the mechanisms that promote local suppression in inflamed tissues will provide critical new insights and opportunities to improve therapeutic manipulations to treat hyper-immune syndromes such as transplant rejection, and autoimmune and allergic diseases by introducing donor (all) and self (auto) antigens at the same time as boosting immune suppressor activity. In previous work, we identified rare populations of plasmacytoid dendritic cells (pDCs) in humans and mice uniquely competent to express the immunosuppressive enzyme indoleamine 2,3 dioxygenase (IDO). In mice, interferon type I (IFN1) was the obligate upstream IDO inducer in splenic IDO-competent pDCs after B7 ligation. However, IFN1 production by pDCs was dependent on IDO activity, revealing that IDO amplified its own expression in IDO-competent pDCs via a cell autonomous IFN1-dependent pathway. Unlike their counterparts in spleen, pDCs in draining lymph nodes (dLNs) associated with melanoma growth expressed IDO constitutively, exhibited potent suppressor activity and activated regulatory CD4+CD25+ T cells (Tregs). We hypothesize that the ability of IDO-competent pDCs to create local suppression is critically dependent on cooperative interactions between pDCs and Tregs that amplify IDO expression, which triggers suppressor activity in both cell types. In preliminary studies we show that topical treatment of mice with the pro-inflammatory reagent and tumor promoter phorbol myristate acetate (PMA) paradoxically creates potent local suppression in skin dLNs by activating pDCs to express IDO, which in turn activate Tregs via IDO. The objective of studies proposed is to elucidate the mechanisms that induce dLN pDCs to express IDO (Aim 1), and activate Treg bystander suppressor activity via IDO (Aim 2) after PMA treatment. New knowledge generated will be used to guide and evaluate innovative methods to enhance local IDO expression during immunization, skin grafting and during autoimmune type I diabetes progression to block T cell mediated destruction of skin allografts and pancreatic islet cells, respectively. PUBLIC HEALTH RELEVANCE Studies proposed focus on a small subset of dendritic cells that completely suppress T cell responses to antigens in inflamed tissues when they receive particular signals from the tissue microenvironment. To create suppressive tissue microenvironments, dendritic cells must interact with a small subset of regulatory T cells via specific signaling pathways. Recently, we discovered that skin inflammation provoked by `painting' with a pro-inflammatory reagent commonly used in mouse models of tumor progression induces potent suppressor activity mediated by dendritic cells in skin draining lymph nodes. This observation provides a rationale for treating mice with donor allograft and self-antigens to induce tolerance that will protect skin grafts and pancreatic islet cells from T cell mediated destruction. 1