Regulation of Liver DC Function and Transplant Tolerance

总结 肝脏显示出固有的致耐受性，并且肝脏同种异体移植物比其他器官更容易促进耐受。 与循环或次级淋巴组织树突状细胞（DC）相比，肝脏常规髓样（m）DC 产生更低的IL-12，分泌更多的IL-10，诱导同种异体抗原特异性T细胞低反应性，并延长 同种异体移植物存活率。肝DC对Toll样受体（TLR）激动和核因子（NF）κβ不敏感 活化，-DC成熟的关键决定因素。潜在的机制可能有助于其监管 功能和肝移植物固有的耐受性。重要的是，我们的新数据显示， 供体mDC的缺失防止小鼠的“自发”肝移植耐受。 在一般DC中，特别是在肝DC中，对TLR激动无反应性的潜在机制， 定义不明确。我们已经鉴定了12 KDa的信号衔接DNA X激活蛋白（DAP 12）， 其可以介导TLR活化的抑制，并且在肝mDC中上调，作为一种关键的新的 调节肝DC功能和肝移植耐受。因此，我们假设， TLR信号转导的调节因子，特别是IL-1 R相关激酶（IRAK）-M（我们发现， 肝mDC中的DAP 12）赋予对成熟的抗性和致耐受性能力。我们进一步假设，反- 肝脏中产生的炎性IL-10和TGFβ通过分子途径增强肝DC的耐受性 它们各自的信号传导途径（TGFβ的Smad和IL-10的STAT 3）和TLR之间的“串扰” 信号通路肝脏mDC的致耐受性功能可能有助于诱导/维持 在面对持续TLR激动和其他促炎刺激时的肝移植耐受性。 我们的研究将使用创新的方法和尖端技术，包括活体成像和 产生新的嵌合供体小鼠肝脏，为分子生物学提供新的机制见解。 肝脏DC功能的调节及其对同种异体反应性T细胞应答和肝移植耐受的影响。我们 还将评估TLR信号传导/肝DC成熟的负调节剂的治疗潜力， 恢复/促进移植耐受性。我们提出以下目标： 目的1：阐明DAP 12和TLR信号的诱导调控在肿瘤发生发展中的作用。 小鼠肝脏mDC耐受性，以及抗炎因子和促炎因子的影响;目的2： 使用创新的体内方法建立供体mDC、TLR 4和DAP 12-IRAK-M的作用 通过肝脏mDC表达控制T细胞应答和对肝脏同种异体移植物的耐受性。

Summary The liver displays inherent tolerogenicity and liver allografts promote tolerance more readily than other organs. Compared to circulating or secondary lymphoid tissue dendritic cells (DC), liver conventional myeloid (m) DC produce lower IL-12, secrete more IL-10, induce alloAg-specific T cell hyporesponsiveness and prolong allograft survival. Liver DC are refractory to Toll-like receptor (TLR) agonism and nuclear factor (NF)κβ activation,- a critical determinant of DC maturation. Underlying mechanisms may contribute to their regulatory function and the inherent tolerogenicity of hepatic allografts. Importantly, our new data show that selective deletion of donor mDC prevents ‘spontaneous’ liver transplant tolerance in mice. Mechanisms underlying unresponsiveness to TLR agonism in DC in general, and in liver DC, in particular, are poorly defined. We have identified the signaling adaptor DNAX-activating protein of 12KDa (DAP12), that can mediate inhibition of TLR activation and that is upregulated in liver mDC, as a critical novel regulator of liver DC function and liver transplant tolerance. Consequently, we hypothesize that negative regulators of TLR signaling, in particular IL-1R-associated kinase (IRAK)-M (that we show is upregulated with DAP12 in liver mDC) confer resistance to maturation and tolerogenic capacity. We further postulate that anti- inflammatory IL-10 and TGFβ, produced in the liver, potentiate liver DC tolerogenicity through molecular ‘crosstalk’ between their respective signaling pathways (Smad for TGFβ and STAT3 for IL-10) and the TLR signaling pathway. The tolerogenic function attributed to liver mDC may contribute to induction/maintenance of liver transplant tolerance in the face of continuous TLR agonism and other pro-inflammatory stimuli. Our studies will use innovative approaches and cutting edge technology, including intravital imaging and generation of novel, chimeric donor mouse livers, to provide new mechanistic insight into the molecular regulation of liver DC function and its impact on alloreactive T cell responses and liver transplant tolerance. We will also evaluate the therapeutic potential of negative regulators of TLR signaling/liver DC maturation for restoration/promotion of transplant tolerance. We propose the following aims: AIM 1: To elucidate the role of DAP12 and inducible regulation of TLR signaling in the development of mouse liver mDC tolerogenicity, and the influence of anti- and pro-inflammatory factors; AIM 2: To establish using innovative in vivo approaches, the roles of donor mDC, TLR4, and DAP12-IRAK-M expression by liver mDC in control of T cell responses and tolerance to liver allografts.