Regulation of conventional versus innate CD8+ T cell development

描述（由申请人提供）：目前已知胸腺中常规与先天性CD 8 + T细胞发育的调节可产生多种不同的T细胞谱系。这些T细胞亚群中的许多在调节对自身以及对病原体的免疫应答中起关键作用。除了常规的CD 4+和CD 8 + T细胞外，T细胞是适应性免疫反应的关键组成部分，有调节性T细胞，NKT细胞，？？T细胞，以及各种额外的先天性T细胞亚群。发育成这些谱系中的每一种的T细胞的适当平衡对于维持免疫稳态、自身耐受性以及对病原性感染产生快速和延迟反应的能力是必不可少的。目前，这些发育谱系选择的分子机制正在紧张的调查。我们自己的研究已经确定了一个涉及Tec家族酪氨酸激酶Itk的信号通路，它决定了传统与先天性CD 8 + T细胞的发育。在具有正常Itk功能的野生型（WT）胸腺细胞中，MHC I类特异性T细胞主要发育成常规幼稚CD 8 + T细胞，其是效应细胞毒性T细胞的前体。此外，一个非常小的细胞亚群发育成先天性CD 8 + T细胞，其具有先前激活的记忆性CD 8 + T细胞的特征，并且在激活时表现出即时效应子功能。与此相反，缺乏Tec激酶Itk的MHC I类特异性胸腺细胞几乎完全发育成表达高水平T盒转录因子Eomesodermin的先天性CD 8 + T细胞。这些发现表明，需要Itk的信号通路调节常规和先天性CD 8 + T细胞之间的谱系决定。众所周知，Itk是TCR信号通路的一个组成部分，导致磷脂酶？31活化和肌动蛋白聚合，这些数据还暗示改变的TCR信号传导是这些关键T细胞谱系决定的调节剂。为了确定这种谱系决定的转录调节因子，我们进行了微阵列实验，以确定WT常规和Itk缺陷先天性CD 8+胸腺细胞之间差异表达的因子。有趣的是，该分析表明，相对于Itk缺陷型CD 8+胸腺细胞，WT中最高度上调的转录因子是IRF 4;此外，我们的初步研究表明，在缺乏IRF 4的情况下，几乎所有的CD 8 + T细胞也发育成先天谱系。相比之下，相对于WT，在Itk缺陷型胸腺细胞中表达最高的转录因子是Runx 2。我们假设Itk信号通过诱导IRF 4的转录促进常规CD 8 + T细胞发育，并且在Itk不存在的情况下，Runx 2上调将常规CD 8 + T细胞转化为先天性T细胞，导致Eomesodermin上调。为了确定这些转录因子在调节常规与先天性CD 8 + T细胞发育中的重要性，我们建议检查IRF 4是否对常规CD 8 + T细胞谱系定型至关重要。我们还将研究IRF 4是否足以抑制CD 8 + T细胞中的Eomesodermin表达。第三，我们将确定不同强度的TCR信号传导是否导致IRF 4的分级表达。最后，我们将研究Runx 2是否是先天性CD 8 + T细胞发育所必需的。 公共卫生相关性：我们的免疫系统使用许多不同类型的白色血细胞保护我们免受各种病原体的侵害。本提案中描述的工作将调查我们的身体如何以正确的比例产生正确类型的白色血细胞。这种理解将有助于调节和控制免疫系统以对抗感染和根除癌细胞。

DESCRIPTION (provided by applicant): Regulation of conventional versus innate CD8+ T cell development in the thymus is now known to produce a wide array of distinct T cell lineages. Many of these T cell subsets play key roles in regulating immune responses, both to self as well as to pathogens. In addition to the conventional CD4+ and CD8+ ???T cells that are key components of the adaptive immune response, there are regulatory T cells, NKT cells, ?? T cells, and a variety of additional innate T cell subsets. The appropriate balance of T cells developing into each of these lineages is essential to maintain immunological homeostasis, self-tolerance, and the ability to produce both rapid and delayed responses to pathogenic infections. Currently, the molecular mechanisms governing these developmental lineage choices are under intense investigation. Our own studies have identified a signaling pathway involving the Tec family tyrosine kinase, Itk, which determines conventional versus innate CD8+ T cell development. In wild-type (WT) thymocytes with normal Itk function, MHC class I-specific T cells predominantly develop into conventional naive CD8+ T cells, which are precursors of effector cytotoxic T cells. In addition, a very minor subset of cells develop into innate CD8+ T cells that have characteristics of previously-activated memory CD8+ T cells, and exhibit immediate effector function when activated. In contrast to this, MHC class I-specific thymocytes lacking the Tec kinase, Itk, develop nearly exclusively into innate CD8+ T cells that express high levels of the T-box transcription factor, Eomesodermin. These findings indicate that a signaling pathway requiring Itk regulates the lineage decision between conventional and innate CD8+ T cells. As Itk is well known as a component of the TCR signaling pathway leading to phospholipase?-31 activation and actin polymerization, these data also implicate altered TCR signaling as a modulator of these key T cell lineage decisions. To determine the transcriptional regulators of this lineage decision, we performed a microarray experiment to identify factors differentially expressed between WT conventional and Itk-deficient innate CD8+ thymocytes. Interestingly, this analysis indicated that the single most highly up-regulated transcription factor in WT relative to Itk-deficient CD8+ thymocytes is IRF4; further, our preliminary studies indicate that in the absence of IRF4, nearly all CD8+ T cells also develop into the innate lineage. In contrast, the transcription factor most highly expressed in Itk- deficient thymocytes relative to WT is Runx2. We hypothesize that Itk signaling promotes conventional CD8+ T cell development by inducing the transcription of IRF4, and that in the absence of Itk, Runx2 upregulation converts conventional CD8+ T cells into innate T cells, leading to upregulation of Eomesodermin. To determine the importance of these transcription factors in regulating conventional versus innate CD8+ T cell development we propose to examine whether IRF4 is essential for conventional CD8+ T cell lineage commitment. We will also investigate whether IRF4 is sufficient to suppress Eomesodermin expression in CD8+ T cells. Third, we will determine whether different strengths of TCR signaling lead to graded expression of IRF4. Finally, we will examine whether Runx2 is required for innate CD8+ T cell development. PUBLIC HEALTH RELEVANCE: Our immune system protects us against a wide array of pathogens using many different types of white blood cells. The work described in this proposal will investigate how our body produces the correct types of white blood cells in the correct proportions. This understanding will aid in efforts to regulate and control the immune system to fight infections and eradicate cancer cells.