Regulation of conventional versus innate CD8+ T cell development

描述(由申请人提供)：现在已知胸腺中传统的和固有的CD8+T细胞发育的调节可以产生一系列不同的T细胞谱系。这些T细胞亚群中的许多在调节自身和病原体的免疫反应方面发挥着关键作用。除了作为获得性免疫反应的关键组成部分的传统的CD4+和CD8+？？T细胞外，还有调节性T细胞、NKT细胞、？？T细胞。T细胞，以及各种额外的先天T细胞亚群。T细胞向这些谱系发展的适当平衡对于维持免疫平衡、自我耐受以及对病原性感染产生快速和延迟反应的能力是至关重要的。目前，控制这些发育谱系选择的分子机制正在深入研究中。我们自己的研究已经确定了一条涉及Tec家族酪氨酸激酶(ITK)的信号通路，它决定了传统的和天然的CD8+T细胞的发育。在ITK功能正常的野生型(WT)胸腺细胞中，MHC-I类特异性T细胞主要发育为传统的单纯CD8+T细胞，是效应性细胞毒性T细胞的前体。此外，极少数细胞亚群发育成天生的CD8+T细胞，具有先前激活的记忆CD8+T细胞的特征，并在激活时表现出即时效应功能。相比之下，缺乏Tec激酶ITK的MHC I类特异性胸腺细胞几乎完全发育成天然的CD8+T细胞，表达高水平的T-box转录因子Eomesodermin。这些发现表明，需要ITK的信号通路调节了传统CD8+T细胞和天然CD8+T细胞之间的谱系决定。众所周知，ITK是导致磷脂酶？-31激活和肌动蛋白聚合的TCR信号通路的一个组成部分，这些数据也暗示TCR信号的改变是这些关键T细胞谱系决定的调节器。为了确定这一谱系决定的转录调控因素，我们进行了一项微阵列实验，以确定WT常规胸腺细胞和ITK缺乏的先天性CD8+胸腺细胞之间的差异表达因子。有趣的是，这一分析表明，与ITK缺乏的CD8+胸腺细胞相比，WT中上调程度最高的单一转录因子是IRF4；此外，我们的初步研究表明，在缺乏IRF4的情况下，几乎所有的CD8+T细胞也发育成先天谱系。相反，与WT相比，在ITK缺陷胸腺细胞中表达最高的转录因子是Runx2。我们假设ITK信号通过诱导IRF4的转录促进常规CD8+T细胞的发育，在没有ITK的情况下，Runx2上调将常规CD8+T细胞转化为固有T细胞，导致Eomesodermin上调。为了确定这些转录因子在调节常规和先天CD8+T细胞发育中的重要性，我们建议检查IRF4是否对常规CD8+T细胞谱系的承诺是必要的。我们还将研究IRF4是否足以抑制CD8+T细胞中Eomesodermin的表达。第三，我们将确定不同强度的TCR信号是否会导致IRF4的分级表达。最后，我们将研究Runx2是否是先天CD8+T细胞发育所必需的。 与公共卫生相关：我们的免疫系统使用许多不同类型的白细胞保护我们免受各种病原体的侵袭。这项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血球。这一认识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.