Understanding thymic acquisition of gamma/delta T cell effector function

Gamma/Delta T细胞对艾滋病毒、流感、结核病和疟疾等感染做出非多余的免疫反应，并在牛皮癣和多发性硬化症等免疫病理中发挥关键作用。此外，伽马/增量T细胞现在被认为是抗癌免疫治疗策略的有吸引力的候选者。事实上，最近对39种不同恶性肿瘤的18,000名癌症患者的研究表明，肿瘤相关的伽马/德尔塔T细胞表达谱是单一最大的阳性预后免疫相关指标。伽玛/德尔塔T细胞主要通过早期提供细胞因子和趋化因子来管理其组织相关效应功能，这些细胞因子和趋化因子既影响局部组织环境，又影响下游α/βT细胞介导的适应性免疫反应。干扰素-伽马和白细胞介素17A的分泌是这一效应功能的中心成分；例如，干扰素-伽马参与抗病毒和抗肿瘤免疫反应，而白细胞介素17A对于清除真菌感染至关重要。尽管表面上类似于(例如表达T细胞受体)α/βT细胞，但伽马/德尔塔T细胞现在被认为有重要的区别。与在免疫反应中只致力于特定效应功能的α/βT细胞不同，伽马/βT细胞在胸腺发育期间获得其效应功能(即产生干扰素-伽马或IL-17A)。推动胸腺对效应器命运的这种承诺的机制过程仍在探索中，但无疑是充分理解伽马/德尔塔T细胞生物学的关键基石。我们最近对伽马/德尔塔T细胞发育的工作导致了以下假设：伽马/德尔塔T细胞受体(TCR)指示伽马/德尔塔祖细胞在胸腺发育期间采用特定的命运；伽玛/德尔塔TCR下游离散信号通路的参与推动对不同的效应者命运的不同承诺，以及；采用适当的代谢程序对于胸腺获得γ/Delta T细胞命运和随后的效应功能至关重要。为了验证这些假说，我们将结合最先进的体外技术(例如胸腺器官培养、单细胞RNA分析、逆转录病毒基因转导)和体内基因缺陷小鼠的研究。在主要目标-1中，我们将评估驱动对不同效应者命运的承诺的伽马/德尔塔TCR的特征(例如，TCR高变区的重要性、所使用的TCR链的亚型、TCR表达的时间以及对激活或抑制配体结合的依赖)。在主要目标-2中，我们将研究离散的信号网络对采用不同的效应器命运的重要性(例如，由PI3-激酶、ERK/MAPK或NF-kappa-B控制的那些)，重点是这些信号网络如何与转录因子网络相互作用。最后，在AIM-3中，我们将评估调节发育中的伽马/德尔塔T细胞的差异代谢编程的机制，以及这如何影响后续的伽马/德尔塔T细胞功能。越来越多的人认为，γ/Delta T细胞将广泛反应、快速起作用的先天免疫系统与病原体特异性适应性免疫系统的延迟反应联系起来。因此，了解获得性免疫的特征(例如TCR表达/信号)如何指导先天性质的获得(例如细胞因子的快速分泌)将特别具有启发性。此外，了解伽马/德尔塔T细胞的发育将提供对伽马/德尔塔T细胞功能的重要洞察。反过来，这将更好地为疾病中伽马/德尔塔T细胞反应的增强提供信息，并将更好地建议如何将这些细胞用于免疫治疗方法，例如在抗肿瘤策略中。

Gamma/delta T cells make non-redundant immune responses to infections such as HIV, influenza, tuberculosis and malaria, and have critical roles in immunopathologies such as psoriasis and multiple sclerosis. Moreover, gamma/delta T cells are now considered attractive candidates for immunotherapy strategies against cancer. Indeed, a recent study of 18,000 cancer patients with 39 different malignancies revealed a tumour-associated gamma/delta T cell expression profile as the single biggest positive prognostic immune-related indicator.Gamma/delta T cells administer their tissue-associated effector functions largely through early provision of cytokines and chemokines that influence both the local tissue environment and downstream alpha/beta T cell-mediated adaptive immune responses. Secretion of interferon gamma (IFN-gamma) and interleukin-17A (IL-17A) are central components to this effector function; for example, IFN-gamma is implicated in anti-viral and anti-tumour immune responses, while IL-17A is critical for clearance of fungal infections.Despite being superficially similar (e.g. expressing a T cell receptor) to alpha/beta T cells, gamma/delta T cells are now recognised as having important differences. Unlike alpha/beta T cells that only commit to specific effector functions during an immune response, gamma/delta T cells acquire their effector function (i.e. to produce IFN-gamma or IL-17A) during development in the thymus. The mechanistic processes that drive this thymic commitment to effector fate are still being explored, but undoubtedly represent a key foundation stone for fully understanding gamma/delta T cell biology.Our recent work on gamma/delta T cell development has led to the following hypotheses; that the gamma/delta T cell receptor (TCR) instructs gamma/delta progenitors to adopt specific fates during thymic development; that engagement of discrete signalling pathways downstream of the gamma/delta TCR drives differential commitment to distinct effector fates, and; that adoption of appropriate metabolic programs is crucial for thymic acquisition of gamma/delta T cell fate and subsequent effector function.To test these hypotheses we will combine state-of-the-art techniques in vitro (e.g. thymus organ cultures, single-cell RNA analyses, retroviral gene transduction) with studies in gene-deficient mice in vivo. In major aim-1, we will assess characteristics of the gamma/delta TCR that drive commitment to distinct effector fates (e.g. importance of the TCR highly variable regions, the sub-type of TCR chain used, the timing of TCR expression, and dependence on binding to activating or inhibitory ligands). In major aim-2, we will examine the importance of discrete signalling networks to adoption of distinct effector fates (e.g. those controlled by PI3-kinase, ERK/MAPK or NF-kappa-B), with emphasis on how these interact with transcription factor networks. Finally, in aim-3 we will assess the mechanisms that regulate the differential metabolic programming of developing gamma/delta T cells and how this impacts on subsequent gamma/delta T cell function.The studies detailed in this proposal will significantly advance the field of gamma/delta T cell biology. Gamma/delta T cells are increasingly considered to connect the broadly reactive, rapidly acting innate immune system with the delayed responses of the pathogen-specific adaptive immune system. Thus, understanding how features of adaptive immunity (e.g. TCR expression/signalling) instruct acquisition of innate-like qualities (e.g. rapid secretion of cytokines) will be particularly illuminating. Moreover, understanding gamma/delta T cell development will provide critical insight into gamma/delta T cell function. In turn, this will better inform augmentation of gamma/delta T cell responses in disease, and will better advise how these cells can be utilized in immunotherapeutic approaches, for example in anti-tumour strategies.