Dendritic Cell Control of Skin Immunity

描述（由申请人提供）： 预防传染病的疫苗接种是预防退伍军人和现役士兵发病和死亡的主要手段。有效的疫苗接种，类似于对感染的免疫应答，需要通过表达MHC II类肽复合物的专职抗原呈递细胞激活CD 4+辅助T细胞。大多数疫苗接种都是皮下注射;因此，了解皮肤中MHC II类依赖性免疫应答的调节将为疫苗的合理设计提供信息。令人惊讶的是，我们发现淋巴驻留和迁移DC的抗原加工和呈递是皮下免疫后CD 4 + T细胞的克隆选择和扩增所必需的。淋巴驻留DC的早期抗原呈递启动了引流LN中抗原特异性T细胞的活化和捕获，而不诱导克隆扩增。然而，迁移性DC与保留在LN中的CD 4 + T细胞相互作用以诱导增殖。因此，不同的DC亚群合作以警告和捕获适当的细胞，然后允许其扩增和分化。这些初步结果引出了一个显而易见的问题：为什么需要两个DC群体来引发CD 4 + T细胞？在目前的建议中，我们将剖析的细胞和分子机制的基础上，需要两个不同的群体的树突状细胞在皮肤中的抗原传递的反应。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缀合的微球来限制抗原呈递给一个DC群体。这将检验限制于迁移性DC的抗原呈递不能引发幼稚CD 4 + T细胞的假设。在我们的后两个目标中，我们将研究两种不同的解释，要求淋巴驻留和迁移DC。首先，免疫荧光和分子技术将被用来解剖与淋巴驻留DC相互作用后的T细胞的定位。我们将考虑LN中的幼稚T细胞必须改变位置以允许与抗原负载的迁移性DC相互作用的假设。最后，我们将确定CD 4 + T细胞的生化设定点和行为后，引发淋巴驻留的DC。T细胞活化是否发生在两个不同的步骤中，由两个不同的DC群体调节？了解CD 4 + T细胞活化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严重疾病的病原体。 公共卫生相关性： 接种疫苗是预防士兵在训练和战争期间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疫苗的有效性和长期安全性，无论是单独提供，如炭疽疫苗接种，或结合士兵。对病原体和疫苗接种的免疫应答依赖于CD 4 + T细胞的活化，这是一种协调免疫应答的白色血细胞。许多疫苗是通过注射到皮肤中来传递的。在目前的建议中，我们表明，两种不同类型的白色血细胞合作，以诱导CD 4 + T细胞对注射到皮肤中的蛋白质的反应。我们将探索使这一复杂途径成为必要的生物学机制。建立一个更好的模式来激活皮肤中的T细胞应该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.