The Regulatory Control Mechanisms of Cross-presentation by Toll-like Receptors

描述(申请人提供)：树突状细胞(DC)协调耐受或免疫。这一重要功能的核心是吞噬作用，它允许DC对组织微环境进行采样，并在一个称为吞噬小体成熟的过程中将其成分输送到内吞体内。吞噬小体成熟的两个重要结果是主要组织相容性复合体(MHC)II类递呈和交叉递呈，这两种递呈分别对CD4和CD8T细胞的激活有重要影响。交叉呈递允许DC从感染或异常的细胞中获得抗原，并安全地协调MHC I类限制性反应。在吞噬过程中，DC基于Toll样受体(Toll-like Receptor，TLR)信号通路的不同参与，建立自我/非自我辨别。我们已经证明，TLRs控制着吞噬小体的成熟及其结果之一，MHC II类递呈。我们目前的提案集中于解决交叉呈现是否也受到监管的问题，交叉呈现依赖于MHC II类呈现所必需的相同内化途径。我们的主要假设是，交叉呈现在多个水平上受到TLRs信号的正向调节。我们的这一假说是基于我们的观察结果，即：1)吞噬小体成熟为加工内细胞室是由TLR信号诱导的；2)MHC II类递送是由TLR控制的；3)吞噬小体是独立的细胞器，根据其货物的性质和来源单独调节MHC II类递送；以及4)我们的新结果表明，在没有TLR信号的情况下，交叉递呈受到损害。我们的长期目标是确定管理树突状细胞内抗原递送途径的调节检查点，允许细胞区分自我和非自我。我们的具体目标是：1.确定TLR信号是否调节交叉呈现。我们将研究TLRs是否控制吞噬的货物形成多肽-MHC-I类复合体，从而控制CD8 T细胞对这些货物来源的抗原的激活。我们将调查这种控制是否在树突状细胞内被分隔地限制在含有TLR配体的吞噬小体上。2.定义MHC II类呈现的TLR控制对交叉呈现的影响。我们将通过确定CD4T细胞帮助的可用性来确定TLRs是否控制CD8T细胞对细胞抗原的反应。这种帮助对于CD8T细胞的正确激活和分化是必要的。 公共卫生相关性免疫系统对人体自身的细胞和组织具有耐受性。这一建议旨在了解启动对微生物病原体免疫的信号如何维持对自身的现有耐受性。我们获得的新知识将进一步设计治疗性抗病毒和抗肿瘤疫苗，并拓宽我们对自身免疫的理解。

DESCRIPTION (provided by applicant): Dendritic cells (DCs) orchestrate either tolerance or immunity. At the heart of this important function lies phagocytosis, which allows DCs to sample the tissue microenvironment and deliver its constituents into endocytic compartments in a process called phagosome maturation. Two important outcomes of phagosome maturation are major histocompatibility complex (MHC) class II presentation and cross-presentation, both of which have important consequences on the activation of CD4 and CD8 T cells, respectively. Cross- presentation allows DCs to acquire antigen from infected or abnormal cells and safely orchestrate MHC class I- restricted responses. During phagocytosis, DCs establish self/non-self discrimination based on the differential engagement of Toll-like receptor (TLR) signaling pathways. We have shown that TLRs control phagosome maturation and one of its consequences, MHC class II presentation. Our current proposal is focused on addressing whether cross-presentation, which relies on the same internalization pathways necessary for MHC class II presentation, is also subject to regulatory control. Our main hypothesis is that cross-presentation is positively regulated by signals from TLRs at multiple levels. We base this hypothesis on our observations that i) phagosome maturation into processing endocytic compartments is induced by TLR signals, ii) MHC class II presentation is controlled by TLRs, iii) phagosomes are autonomous organelles that individually regulate MHC class II presentation depending on the nature and origin of their cargo, and iv) our new results indicate that cross-presentation is impaired in the absence of TLR signals. Our long-term goal is to identify regulatory checkpoints that govern antigen presentation pathways within DCs, allowing cellular discrimination between self and non-self. Our specific aims are to: 1. Determine whether TLR signals regulate cross-presentation. We will investigate whether TLRs control formation of peptide-MHC class I complexes from phagocytosed cargo and thereby CD8 T cell activation to antigens derived from these cargos. We will investigate whether this control is compartmentally restricted within DCs to phagosomes that contain TLR ligands. 2. Define the consequences of TLR control of MHC class II presentation on cross-presentation. We will determine whether TLRs control CD8 T cell responses to cellular antigens by determining the availability of CD4 T cell help. This help is necessary for the proper activation and differentiation of CD8 T cells. PUBLIC HEALTH RELEVANCE The immune system is tolerant to the body's own cells and tissues. This proposal aims to understand how signals that initiate immunity to microbial pathogens maintain the existing tolerance to self. The new knowledge we gain will further the design of therapeutic anti-viral and anti-tumor vaccines, and broaden our understanding of autoimmunity.