Dynamic regulation of human immunity by Interferon Regulatory Factor 8 (IRF8)

免疫系统是我们抵御细菌感染、病毒和癌症的主要防御系统。它也是炎症性疾病的罪魁祸首，在与年龄相关的退行性疾病中发挥着重要作用。免疫系统由许多不同的细胞组成，包括粒细胞、单核细胞、树突状细胞和淋巴细胞。所有这些都是由干细胞通过造血过程在骨髓中创造出来的，也就是所谓的造血。这项研究项目旨在了解造血是如何控制免疫反应的。不同细胞的产生依赖于特定的基因，这些基因由与DNA结合的蛋白质启动和关闭，这些蛋白质被称为转录因子。生产经过微调，使免疫系统能够对特定的威胁做出反应，这一过程被称为需求适应。干扰素调节因子8(IRF8)是造血中的关键转录因子，但它是如何调控的，以及它是如何控制其他基因的，目前还不清楚。我之前发现，IRF8基因有缺陷的人不能产生树突状细胞，在某些情况下也不能产生单核细胞，但有大量过剩的中性粒细胞。这种不平衡程度取决于存在多少IRF8活动，这强烈表明IRF8是主控制开关。如果没有足够的树突状细胞，那么就不可能对过去的病毒感染和疫苗形成免疫记忆。缺乏中性粒细胞会导致频繁的、往往是致命的细菌感染，而太多的中性粒细胞会导致肺部炎症，抑制对癌症的自然免疫反应。因此，正确平衡的造血对于保持健康和有效应对疾病至关重要。在这个项目中，我将研究IRF8是如何调节的，以及它如何通过控制其他基因的活性来维持造血平衡。我将使用尖端技术来揭示单个细胞内的这些过程。我还将利用IRF8基因的遗传变异来研究个体之间的差异如何影响免疫力。该项目有四个目标。在第一个目标中，我将使用单细胞技术来绘制免疫细胞的发育途径，识别这些途径中对调节IRF8重要的DNA区域，并定义IRF8控制的基因。在目标2中，我将扩展这些技术来分析感染引起的败血症患者或乳腺癌患者的造血干细胞，这两种情况都与免疫细胞极度失衡有关。这将使我能够确定导致失衡的机制，并找到控制这些机制的方法，以获得医疗利益。在目标3中，我将收集IRF8基因严重突变的人的样本，以了解IRF8的不同部分是如何正确发挥作用的。最后，在目标4中，我将研究IRF8基因区域的自然遗传变异，以创建如何控制IRF8基因活性的详细地图。很可能，作为一个种群，我们有广泛的IRF8反应，这种遗传变异使我们作为一个物种在面临感染和其他挑战时具有多样性。总之，这项工作将确定IRF8在人类造血中的确切作用，以及这种作用如何控制免疫细胞的发育。我将发现控制IRF8的因素，并绘制免疫细胞发育每个阶段中受IRF8影响的基因网络。这将确定修改造血功能以实现对感染、疫苗和免疫治疗的更好免疫反应、抑制有害免疫反应和增强对癌症的免疫力的方法。

The immune system is our major defence against bacterial infections, viruses and cancer. It is also responsible for inflammatory diseases and plays a major role in age-related degenerative diseases. The immune system is made of many different cells including granulocytes, monocytes, dendritic cells and lymphocytes. All of these are created in the bone marrow from stem cells through the process of blood formation, known as haematopoiesis. This research project aims to understand how haematopoiesis controls immune responses.Haematopoiesis is a complex process. The production of different cells depends upon specific genes that are turned on and off by proteins that bind to DNA, known as transcription factors. Production is finely tuned to allow the immune system to respond to specific threats, a process known as demand-adaptation. Interferon Regulatory Factor 8 (IRF8) is a key transcription factor in haematopoiesis but how it is regulated and how it controls other genes is not well understood. I have previously found that people with a faulty IRF8 gene are unable to make dendritic cells, and in some cases also monocytes, but have a large excess of neutrophils. The level of imbalance depends upon how much IRF8 activity is present, strongly suggesting that IRF8 is the master control switch. If there are insufficient dendritic cells, then it is not possible to develop immune memory to past viral infections and vaccines. Lack of neutrophils lead to frequent and often fatal bacterial infections, while too many can cause inflammation in the lungs and suppress natural immune responses to cancer. Correctly balanced haematopoiesis is therefore critical to maintaining health and responding effectively to disease.In this project I will study how IRF8 is regulated and how it maintains the balance of haematopoiesis by controlling the activity of other genes. I will use cutting-edge techniques that reveal these processes within single cells. I will also use genetic variation in the IRF8 gene to study how differences between individuals affect immunity.The project has four Aims. In the first Aim, I will use single cell techniques to map the developmental pathways of immune cells, identify regions of DNA important for regulating IRF8 in these pathways, and define the genes that IRF8 controls. In Aim 2, I will extend these techniques to analyse haematopoietic stem cells from patients with sepsis caused by infection, or those with breast cancer, conditions that are both associated with extreme imbalance of immune cells. This will allow me to identify the mechanisms that drive the imbalance and find ways that these could be controlled for medical benefit. In Aim 3, I will gather samples from people with severe mutations in the IRF8 gene in order to understand how different parts of IRF8 are required for it to function correctly. Finally, in Aim 4, I will study natural genetic variation in the region of the IRF8 gene to create a detailed map of how the activity of the IRF8 gene is controlled. It is likely that as a population, we have a wide range of IRF8 responses and that genetic variation gives us diversity as a species in the face of infection and other challenges. Together, this work will define the precise role of IRF8 in human haematopoiesis and how this controls immune cell development. I will discover the factors that control IRF8 and map the network of genes influenced by IRF8 in at each stage of immune cell development. This will identify ways to modify haematopoiesis to achieve better immune responses to infections, vaccines and immune therapy, to suppress harmful immune reactions, and to augment immunity to cancer.