Regulation of Liver DC Function and Transplant Tolerance

摘要 肝脏表现出固有的耐受性，而同种异体肝移植比其他器官更容易促进耐受性。 与循环或次级淋巴组织树突状细胞(DC)相比，肝脏常规髓系(M)DC 产生较低的IL-12，分泌更多的IL-10，诱导同种异体抗原特异性T细胞低反应并延长 同种异体移植物存活率。肝树突状细胞对Toll样受体激动剂和核因子κβ耐药 激活--DC成熟的关键决定因素。潜在的机制可能有助于它们的监管 同种异体肝移植的功能和固有耐受性。重要的是，我们的新数据显示，选择性 供体MDC的缺失可防止小鼠“自发”的肝移植耐受。 DC对TLR激动剂无反应的潜在机制，特别是在肝脏DC中， 是定义不清的。我们已经鉴定出12 KDa的信号转接子DNAX激活蛋白(DAP12)， 它可以介导抑制TLR的激活，并在肝脏MDC中上调，作为一种批判性新书 肝树突状细胞功能调节与肝移植耐受因此，我们假设负面的 TLR信号的调节者，特别是IL-1R相关激酶(IRAK)-M(我们显示上调与 肝脏MDC中的DAP12)具有抗成熟和耐受能力。我们进一步假设，反- 肝脏产生的炎性IL-10和转化生长因子β通过分子机制增强肝脏DC耐受性 它们各自的信号通路(转化生长因子β的Smad和IL-10的STAT3)与TLR3之间的“串扰” 信号通路。肝脏MDC的耐受功能可能有助于诱导/维持 面对持续的TLR激动和其他促炎刺激的肝移植耐受性。 我们的研究将使用创新的方法和尖端技术，包括体内成像和 产生新的嵌合供体小鼠肝脏，为分子机制提供新的见解 肝脏DC功能的调节及其对同种异体反应性T细胞反应和肝移植耐受的影响。我们 还将评估TLR信号/肝脏DC成熟的负调控因子对 恢复/促进移植耐受性。我们提出以下目标： 目的1：阐明DAP12及其对TLR信号的诱导调控在糖尿病的发生发展中的作用。 小鼠肝脏MDC耐受性及抗炎和促炎因子的影响 利用体内创新方法，建立供体MDC、TLR4和DAP12-IRAK-M的作用 肝MDC在控制T细胞反应和肝移植耐受中的表达。

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.