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式已经建立。矛盾的是，越来越多的证据表明，某些形式的炎症会产生局部抑制，特别是在遭受持续感染和发展中的肿瘤引起的慢性炎症的组织中。在免疫能力强的个体中，抑制性炎症可能通过抑制T细胞对肿瘤和病原体抗原的反应以及相关的引流淋巴结，促进肿瘤进展和病原体持续存在。然而，在炎症组织中产生和维持局部抑制的潜在机制尚不清楚。阐明炎症组织中促进局部抑制的机制将提供重要的新见解和机会，通过引入供体（所有）和自身（自身）抗原，同时增强免疫抑制活性，改善治疗超免疫综合征（如移植排斥、自身免疫和过敏性疾病）的治疗方法。在之前的工作中，我们在人类和小鼠中发现了罕见的浆细胞样树突状细胞（pDCs）群体，它们具有独特的表达免疫抑制酶吲哚胺2,3双加氧酶（IDO）的能力。在小鼠实验中，干扰素I型（IFN1）是B7结扎后脾脏IDO-competent pDCs的专性上游IDO诱导剂。然而，pDCs产生IFN1依赖于IDO活性，这表明IDO通过细胞自主的IFN1依赖途径在IDO胜任的pDCs中扩增自身表达。与脾脏中的pDCs不同，与黑色素瘤生长相关的引流淋巴结（dln）中的pDCs组成性地表达IDO，表现出强大的抑制活性，并激活调节性CD4+CD25+ T细胞（Tregs）。我们假设IDO-competent pDCs产生局部抑制的能力严重依赖于pDCs和treg之间的合作相互作用，这些相互作用可以放大IDO表达，从而在两种细胞类型中触发抑制活性。在初步研究中，我们发现用促炎试剂和肿瘤启动剂肉豆蔻酸酯（PMA）局部治疗小鼠，矛盾的是，通过激活pDCs表达IDO，从而激活Tregs，从而在皮肤dln中产生有效的局部抑制。这些研究的目的是阐明PMA治疗后诱导dLN pDCs表达IDO （Aim 1）和通过IDO激活Treg旁观者抑制因子活性（Aim 2）的机制。所产生的新知识将用于指导和评估创新方法，分别在免疫、皮肤移植和自身免疫性I型糖尿病进展期间增强局部IDO表达，以阻断T细胞介导的同种异体皮肤移植和胰岛细胞的破坏。公共卫生相关研究建议关注一小部分树突状细胞，当它们接收来自组织微环境的特定信号时，它们完全抑制炎症组织中T细胞对抗原的反应。为了创建抑制性组织微环境，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，我们发现用一种常用于肿瘤进展小鼠模型的促炎试剂“涂敷”引起的皮肤炎症可诱导由皮肤引流淋巴结中的树突状细胞介导的有效抑制活性。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性提供了理论依据，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