Liver Dendritic Cells in Tolerance and Immunity

描述（由申请人提供）：肝脏具有独特的免疫特性。尽管树突状细胞（DC）被认为是免疫系统的关键调节因子，但对正常肝脏DC知之甚少。我们已经确定，大鼠肝脏DC在功能上不同于大鼠脾脏DC。我们还鉴定了5种新分离的肝DC亚型。一种亚型是浆细胞样DC，我们发现与脾脏相比，它在肝脏中相对丰富。我们发现肝脏和脾脏浆细胞样DC具有不同的功能。稳定状态的肝浆细胞样DC不太成熟，诱导的同种异体和抗原特异性T细胞活化较少。刺激后，肝浆细胞样DC分泌大量tnf - α和ifn - α，而脾浆细胞样DC分泌大量IL-10。我们假设肝浆细胞样DC通常有助于肝脏的耐受性。然而，由于肝浆细胞样DC可以被刺激分泌促炎细胞因子，我们假设它们也能够诱导免疫。在Aim 1中，我们将确定肝浆细胞样DC与T细胞相互作用的机制。我们将采用已建立的TCR转基因T细胞静脉过继转移和足垫注射树突状细胞的小鼠模型。我们将通过研究辅助性T细胞反应和延迟型超敏反应来确定肝浆细胞样DC是否诱导T细胞激活、缺失或抑制。在Aim 2中，我们将通过建立将抗原负载的肝浆细胞样DC注射到小鼠门静脉的模型，来确定肝浆细胞样DC是否对肝脏耐受是必要的。我们还将通过消耗抗体直接测试肝浆细胞样DC在体内门静脉耐受中的重要性。在Aim 3中，我们将研究受刺激的肝浆细胞样DC与T细胞相互作用的机制以及DC细胞因子分泌对其的影响。我们将确定刺激肝浆细胞样DC是否会阻止它们诱导耐受。所提出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，并推进我们对耐受性和免疫的理解。我们希望这一发现对包括自身免疫、感染、移植和癌症在内的肝脏免疫状况具有重要意义。

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.