Liver Dendritic Cells in Tolerance and Immunity

描述(申请人提供)：肝脏的免疫学特性是独一无二的。尽管树突状细胞(DC)是免疫系统的关键调节细胞，但人们对正常肝脏DC知之甚少。我们已经确定小鼠肝脏DC与小鼠脾DC在功能上是不同的。我们还鉴定了5种新分离的肝树突状细胞亚型。其中一个亚型是浆细胞样树突状细胞，我们发现与脾相比，它在肝脏中相对丰富。我们发现肝和脾的浆细胞样树突状细胞具有不同的功能。稳定状态的肝浆细胞样树突状细胞成熟程度较低，诱导的同种异体T细胞和抗原特异性T细胞活性较低。肝脏浆细胞样树突状细胞在刺激时分泌大量的肿瘤坏死因子-α和干扰素-α，而不同于脾浆细胞样树突状细胞分泌大量的IL-10。我们假设肝脏浆细胞样树突状细胞通常有助于肝脏的耐受。然而，由于肝浆细胞样树突状细胞可以被刺激分泌促炎细胞因子，我们推测它们也能够诱导免疫。在目标1中，我们将确定肝浆细胞样树突状细胞与T细胞相互作用的机制。我们将采用建立的小鼠静脉过继转移TCR转基因T细胞和足垫注射树突状细胞的模型。我们将通过研究T辅助反应和迟发性超敏反应来确定肝浆细胞样树突状细胞是否诱导T细胞无能、缺失或抑制。目的2通过建立小鼠门静脉注射抗原负载的肝浆细胞样树突状细胞模型，探讨肝浆细胞样树突状细胞是否是肝耐受所必需的。我们还将使用耗竭抗体在体内直接测试肝浆细胞样树突状细胞在门静脉耐受中的重要性。在目标3中，我们将研究刺激的肝浆细胞样树突状细胞与T细胞相互作用的机制以及DC细胞因子的分泌对其的影响。我们将确定刺激肝脏浆细胞样树突状细胞是否会阻止它们诱导耐受。拟议的实验将进一步定义肝脏树突状细胞的生物学及其与T细胞的相互作用，并促进我们对耐受和免疫的理解。我们希望这些发现对肝脏的免疫学状况有重要意义，包括自身免疫、感染、移植和癌症。

DESCRIPTION (provided by applicant): The liver is unique in its immunologic properties. Although dendritic cells (DC) are known to be critical regulators of the immune system, little is known about normal liver DC. We have determined that bulk murine liver DC are functionally distinct from bulk spleen DC. We have also identified 5 subtypes of freshly isolated liver DC. One subtype is plasmacytoid DC, which we found to be relatively abundant in the liver as compared to the spleen. We have discovered that liver and spleen plasmacytoid DC have disparate function. Steady state liver plasmacytoid DC are less mature and induce less allogeneic and antigen specific T cell activation. Upon stimulation, liver plasmacytoid DC secrete large amounts of TNF-alpha and IFN-alpha unlike spleen plasmacytoid DC, which make large quantities of IL-10. We hypothesize that liver plasmacytoid DC normally contribute to tolerance in the liver. However, because liver plasmacytoid DC can be stimulated to secrete pro-inflammatory cytokines, we postulate that they are also capable of inducing immunity. In Aim 1, we will determine the mechanism of interaction between liver plasmacytoid DC and T cells. We will employ an established murine model of intravenous adoptive transfer of TCR transgenic T cells and footpad injection of dendritic cells. We will determine if liver plasmacytoid DC induce T cell anergy, deletion, or suppression by studying the T helper response and delayed type hypersensitivity reaction. In Aim 2, we will ascertain whether liver plasmacytoid DC are necessary for liver tolerance by developing a model of injecting antigen loaded liver plasmacytoid DC into the portal vein of mice. We will also directly test the importance of liver plasmacytoid DC in portal vein tolerance in vivo by using a depleting antibody. In Aim 3, we will study the mechanism of interaction between stimulated liver plasmacytoid DC and T cells and how it is affected by DC cytokine secretion. We will determine whether stimulation of liver plasmacytoid DC prevents their induction of tolerance. The proposed experiments will define further the biology of liver dendritic cells and their interaction with T cells, as well as advance our understanding of tolerance and immunity. We expect the findings to be important for immunologic conditions of the liver that include autoimmunity, infection, transplantation, and cancer.