Regulation of Innate Dendritic Cell CTLA-4

摘要 髓系树突状细胞(DC)是天然免疫的关键谱系，是主要的接触点和 免疫系统的先天手臂和适应性手臂之间的串扰。CTLA-4是最具特点的 在免疫检查点蛋白中，用于平衡、调节和微调免疫激活的分子 有内环境平衡抑制。CTLA-4由所有主要的淋巴系效应器表达；然而，它的功能- Ality在T细胞中表现得最好，它既表现出细胞外的调节功能，也表现出细胞内的调节功能。 特兹。直到最近，人们对CTLA-4在非淋巴样细胞类型中的表达或功能知之甚少。 尤其是髓系树突状细胞亚群。在此续订应用程序的原始迭代中，我们提供了 初步数据显示，DC分泌的CTLA-4+外切体可以旁分泌方式与B7结合， 囊泡内化和随后内化的旁观者DC中B7表达的下调 CTLA-4+外切体。相反，敲除DC表达的CTLA-4导致显著上调 体外共培养的CD8+细胞的增殖以及体内增强的抗肿瘤和抗病毒免疫。这些 髓系CTLA-4表达的发现和伴随的特征标志着 理解CTLA-4的S在免疫调控中的作用以及天然和 出现自适应串扰。随后的数据表明，DC CTLA-4的表达作为响应被调制 在DC中的这种调节似乎部分受转录因子GATA3的控制 和C/EBP-b。此外，在C57BL/6背景下有条件地消融CTLA-4揭示了潜在的新作用 在胸腺和包括Peyer‘s在内的其他淋巴组织中的调节过程中，DC表达CTLA-4 帕奇斯。这些新颖而令人兴奋的数据使人们得以提出一个精炼的总体假设，即DC- 分泌型CTLA-4+外切体作为效应载体，影响适应性重组的下游极化。 响应由DC检测到的固有信号线索决定。通过三个独立的目标，我们将测试 这一总体假设通过以下方式：1)定义了极化线索在DC CTLA-4表达的治理中的作用- SION与CEBP/b和GATA3转录调控因子的管理，II)确定机制 DC分泌的CTLA-4+和CTLA-4neg外切体通过其调节下游适应性TH极化， 以及iii)定义DC CTLA-4表达通过询问 CD11c-CRE CTLA-4FLOX/FLOX C57BL/6小鼠中观察到调节性T细胞缺陷。完成这些索引- 悬而未决的AIMS将进一步阐明髓系CTLA-4的新调节作用，进一步提高合成 有效和强大的疫苗接种策略，同时确定关键的可用药靶相互作用和免疫 提高对复杂生物途径的理解。

Abstract Myeloid dendritic cells (DC) are a critical lineage of innate immunity that serve as a principal point of contact and crosstalk between the innate and adaptive arms of the immune system. CTLA-4 is one of the best characterized of the immune checkpoint proteins, molecules that serve to balance, regulate, and fine-tune immune activation with homeostatic inhibition. CTLA-4 is expressed by all major lymphoid lineage effectors; however, its function- ality has been best characterized in T-cells where it exhibits both cell-extrinsic and cell-intrinsic regulatory func- tions. Until recently, very little was known about CTLA-4 expression or function in non-lymphoid cell types, par- ticularly the myeloid lineage dendritic cell subsets. In the original iteration of this renewal application, we provided preliminary data demonstrating that DC-secreted CTLA-4+ exosomes could bind B7 in paracrine fashion, leading to vesicle internalization and subsequent downregulation of B7 expression among bystander DC that internalized the CTLA-4+ exosomes. Conversely, knockdown of DC-expressed CTLA-4 resulted in a dramatic upregulation of co-cultured CD8+ cell proliferation in vitro as well as enhanced antitumor and antiviral immunity in vivo. These discoveries and concomitant characterization of myeloid CTLA-4 expression signified a paradigm shift in the understanding of CTLA-4’s role in immune governance as well as the mechanisms through which innate and adaptive crosstalk occur. Subsequent data indicated that the expression of DC CTLA-4 is modulated in response to TH polarizing cues and that regulation in DC appears to be governed in part by the transcription factors GATA3 and C/EBP-b. Further, conditional ablation of CTLA-4 in the C57BL/6 background revealed potential new roles for DC expressed CTLA-4 in regulatory processes in the thymus and in other lymphoid tissues including Peyer’s patches. These novel and exciting data have allowed formulation of a refined overarching hypothesis that DC- secreted CTLA-4+ exosomes act as effector vehicles that shape downstream TH polarization of adaptive re- sponses as dictated by DC detection of innate signaling cues. By means of three independent aims we will test this overarching hypothesis by i) defining the role of TH polarizing cues in the governance of DC CTLA-4 expres- sion and the governance of the CEBP/b and GATA3 transcriptional regulators, ii) defining the mechanisms through which DC-secreted CTLA-4+ and CTLA-4neg exosomes regulate downstream adaptive TH polarization, and iii) defining the manner by which DC CTLA-4 expression modulates central tolerance by interrogating the regulatory T-cell deficits observed in the CD11c-Cre CTLA-4flox/flox C57BL/6 mouse. Completion of these inde- pendent aims will further elucidate the novel regulatory role of myeloid CTLA-4, furthering the ability to synthesize effective and powerful vaccination strategies while characterizing critical druggable target interactions and en- hancing the understanding of complex biological pathways.