Epithelia Associated Dendritic Cells: Phenotype and Function

描述(申请人提供)：树突状细胞(DC)是一种强大的抗原提呈细胞，在启动和引导针对肠道病原体和非病原体的免疫反应中发挥重要作用。最近使用显微镜技术的研究表明，肠道中含有一群DC，它们独特地位于宿主与环境的交界处。这些树突状细胞将树突延伸到肠腔内以采样并对刺激做出反应，由于它们的物理位置，这些树突状细胞具有巨大的潜力来影响免疫反应。尽管有这些开创性的观察，但直接评估DC人群的研究还很缺乏。这些细胞的功能在很大程度上是从相关DC群体的研究中推断出来的，也是从体外用上皮细胞条件培养液处理的DC的研究中推断出来的。此外，这个DC群体的表型多样性几乎完全没有被探索过。在这项建议中，我们将定义来自小鼠和人类小肠的上皮相关树突状细胞(EA-DC)的表型和功能多样性。这一建议的主要假设是，肠道EA-DC包括两种亚型的DC，具有两种不同的表型和功能，炎症性DC和耐受性DC。这些树突状细胞从固有层(LP)迁移到上皮细胞，分别对致病或非致病信号做出反应，包括食物中的维生素A，然后迁移到肠系膜淋巴结(MLN)，启动依赖维生素A的黏膜适应性免疫反应。在具体目标1中，我们将定义小鼠和人类EA-DC群体的表型和功能多样性。这些研究将用流式细胞术评估这群细胞，以确定EA-DC亚型，并检查这些细胞的Toll样受体和趋化因子受体的表达。这些EA-DC亚型的形态将用电子显微镜进行评估。这些DC亚型的功能将通过评估这些细胞印记淋巴细胞的肠道归巢、诱导IgA类转换以及刺激和分化T淋巴细胞的能力来研究。EA-DC亚型的物理位置将在非致病性和致病性感染模型中进行评估。在具体目标2中，我们将通过评估EA-DC亚型来确定膳食维生素A在建立EA-DC生态位和EA-DC功能中的作用。我们将评估膳食维生素A来源对EA-DC粘膜特定功能的作用，并评价膳食维生素A在改变DC表型以占据EA生态位中的作用。树突状细胞是启动和引导免疫反应特征的最强大的免疫细胞，因此在抵抗感染和防止有害免疫反应方面发挥着重要作用。肠道含有独特的树突状细胞群，我们对此知之甚少。这项研究将增加我们对这些树突状细胞如何工作来保护我们免受肠道感染和防止有害免疫反应的了解。

DESCRIPTION (provided by applicant): Dendritic cells (DCs) are potent antigen presenting cells that play an essential role initiating and guiding immune responses toward intestinal pathogens and non-pathogens. Recent studies using microscopy techniques demonstrated that the intestine contains a population of DCs that are uniquely positioned at the interface of the host with the environment. These DCs extend dendrites into the intestinal lumen to sample and respond to stimuli and because of their physical location these DCs have great potential to influence immune responses. Despite these seminal observations, studies directly assessing this DC population are lacking. The function of these cells is largely inferred from studies of related DC populations, and from studies of in vitro derived DCs treated with epithelial cell conditioned media. Furthermore the phenotypic diversity of this DC population is almost completely unexplored. In this proposal we will define the phenotypic and functional diversity of epithelium associated dendritic cells (EA-DC) from the mouse and human small intestine. The overarching hypothesis of this proposal is that intestinal EA-DC include two subtypes of DCs with dichotomous phenotypes and functions, inflammatory DCs and tolerogenic DCs. These DCs migrate from the lamina propria (LP) to become closely associated with the epithelium in response to pathogenic or non- pathogenic signals respectively, sample lumenal stimuli, including dietary vitamin A, and subsequently migrate to mesenteric lymph nodes (MLN) to initiate vitamin A dependent mucosal adaptive immune responses. In specific aim 1 we will define the phenotypic and functional diversity of the murine and human EA-DC population. These studies will evaluate this population of cells with flow cytometry to define the EA-DC subtypes and examine these cells for the expression of toll like receptors and chemokine receptors. The morphology of these EA-DC subtypes will be evaluated with electron microscopy. The function of these DC subtypes will be investigated by evaluating the ability of these cells to imprint gut homing of lymphocytes, induce IgA class switch, and stimulate and differentiate T-lymphocytes. The physical location of the EA-DC subtypes will be evaluated in models of non-pathogenic and pathogenic infections. In specific aim 2 we will define the role of dietary vitamin A in establishing the EA-DC niche and in EA-DC function by evaluating the EA-DC subtypes for the expression of specialized molecular machinery for the uptake and storage of dietary vitamin A. We will evaluate the role of dietary source of vitamin A for mucosal specific functions of the EA-DC, and we will evaluate a role for dietary vitamin A in altering DC phenotype to occupy the EA niche. Dendritic cells are the most powerful immune cells for starting and guiding the character of immune responses, thus these cells play important roles in defending against infections and in preventing unwanted harmful immune responses. The intestine contains unique populations of dendritic cells that we know very little about. This study will increase our knowledge about how these dendritic cells work to protect us from intestinal infections and prevent unwanted harmful immune responses.