Dendritic Cell Control of Skin Immunity

描述(由申请人提供)： 接种传染病疫苗是预防退伍军人和现役士兵发病率和死亡率的主要工具。有效的疫苗接种，类似于对感染的免疫反应，需要表达MHC-II-肽复合体的专业抗原提呈细胞激活CD4+辅助T细胞。大多数疫苗是皮下接种的；因此，了解皮肤中MHC II类依赖的免疫反应的调节将为疫苗的合理设计提供信息。令人惊讶的是，我们发现，在皮下免疫后，CD4+T细胞的克隆性选择和扩增需要淋巴样树突状细胞和迁移性DC的抗原处理和提呈。淋巴样树突状细胞的早期抗原呈递启动了抗原特异性T细胞在引流层核的激活和捕获，而不会引起克隆性扩张。然而，迁移性DC与保留在LN中的CD4+T细胞相互作用以诱导增殖。因此，不同的DC亚群相互协作，以警示和捕获适当的细胞，然后许可其扩展和分化。这些初步结果引出了一个显而易见的问题：为什么启动CD4+T细胞需要两个DC群体？在目前的提案中，我们将剖析两种不同群体的树突状细胞对皮肤递送抗原的反应所依据的细胞和分子机制。我们有三个具体目标。在我们的第一个目标中，我们将利用大的抗原结合微球来限制抗原呈递到一个DC群体。这将检验一种假设，即仅限于迁移性DC的抗原提呈不能激活NAVE CD4+T细胞。在我们的第二个两个目标中，我们将研究对淋巴常驻DC和迁移性DC的要求的两种替代解释。首先，免疫荧光和分子技术将被用来分析T细胞与淋巴树突状细胞相互作用后的定位。我们将考虑这样的假设，即LN中的NAOVE T细胞必须改变位置，以允许与抗原负载的迁移性DC相互作用。最后，我们将确定驻留淋巴的树突状细胞启动后CD4+T细胞的生化设定点和行为。T细胞的激活是否在两个不同的DC群体调控下分两个不同的步骤发生？了解激活CD4+T细胞的要求将指导开发更有效的疫苗，以对抗导致士兵和退伍军人重大疾病的病原体。 公共卫生相关性： 在训练和战争期间，接种疫苗一直是预防士兵发病和死亡的主要机制。然而，退伍军人和他们的医生仍然担心单独接种疫苗的有效性和长期安全性，比如炭疽疫苗接种，或者联合接种给士兵。对病原体和疫苗的免疫反应都依赖于CD4+T细胞的激活，这是一种协调免疫反应的白细胞。许多疫苗是通过注射到皮肤中来注射的。在目前的研究方案中，我们展示了两种不同类型的白细胞协同作用，以诱导CD4+T细胞对注射到皮肤中的蛋白质产生反应。我们将探索使这一复杂途径成为必要的生物机制。建立一个更好的激活皮肤T细胞的范例应该会指导改进疫苗的开发，并改善士兵和退伍军人的健康。

DESCRIPTION (provided by applicant): Vaccination against infectious diseases is a major tool for prevention of morbidity and mortality for both veterans and active-duty soldiers. Effective vaccination, similar to the immune response to infection, requires activation of CD4+ helper T cells by professional antigen presenting cells expressing MHC class II-peptide complexes. Most vaccinations are delivered subcutaneously; thus, understanding the regulation of MHC class II- dependent immune responses in the skin will inform the rational design of vaccines. Surprisingly, we found that antigen processing and presentation by both lymphoid- resident and migratory DCs was required for clonal selection and expansion of CD4+ T cells following subcutaneous immunization. Early antigen presentation by lymphoid- resident DCs initiated activation and trapping of antigen-specific T cells in the draining LN, without inducing clonal expansion. Migratory DCs, however, interact with the CD4+ T cells retained in the LN to induce proliferation. Therefore, distinct DC subsets cooperate to alert and trap the appropriate cell and then license its expansion and differentiation. These preliminary results lead to the obvious question: why are two DC populations necessary to prime CD4+ T cells? In the current proposal, we will dissect the cellular and molecular mechanisms that underlie the requirement for two distinct populations of dendritic cells in the response to antigens delivered in the skin. We have three Specific Aims. In our first Aim, we will utilize large antigen-conjugated microspheres to limit antigen presentation to one population of DCs. This will test the hypothesis that antigen presentation restricted to migratory DCs cannot prime naove CD4+ T cells. In our second two Aims, we will examine two alternative explanations for the requirement for both lymphoid-resident and migratory DCs. First, immunofluorescence and molecular techniques will be utilized to dissect the localization of T cells following interaction with lymphoid-resident DCs. We will consider the hypothesis that naove T cells in the LN must change location to permit interaction with antigen-loaded migratory DCs. Finally, we will determine the biochemical setpoint and behavior of CD4+ T cells following priming by lymphoid-resident DCs. Does T cell activation occur in two distinct steps regulated by two different DC populations? Understanding the requirements for activation of CD4+ T cells will guide the development of more effective vaccinations against pathogens that cause significant disease in soldiers and veterans. PUBLIC HEALTH RELEVANCE: Vaccination has been a major mechanism for prevention of soldier morbidity and mortality during training and war. Yet, veterans and their physicians remain concerned about the efficacy and longterm safety of vaccinations delivered either individually, such as anthrax vaccination, or in combination to soldiers. The immune response to both pathogens and vaccinations rely on activation of CD4+ T cells, a white blood cell that orchestrates the immune response. Many vaccines are delivered by injection into the skin. In the current proposal, we show that two different types of white blood cells collaborate to induce CD4+ T cell responses to proteins injected into the skin. We will explore the biologic mechanisms that make this complex pathway necessary. Establishing a better paradigm for the activation of T cells in the skin should guide the development of improved vaccines and improve the health of both soldiers and veterans.