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

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.