Title: The role of low density granulocytes in the pathogenesis of anti-neutrophil cytoplasm antibody associated vasculitis
Funder: The Academy of Medical Sciences

Abstract: I aim to phenotype granulocyte subsets including low density granulocytes (LDG) in patients with AAV and investigate how LDG contribute to disease pathogenesis. The objectives of the proposal are: 1.Identify and phenotype LDG and normal density neutrophils (NDG) in patients with AAV using, multi-parameter flow cytometry and correlate subsets with disease activity, response to treatment and relapse rate. I will use Nanostring to identify transcriptional differences between LDG and NDG, and imagestream flow cytometry, light and electron microscopy to identify morphological phenotypes 2.Investigate function of LDG in vitro, including cytokine and ROS production in response to ANCA stimulation, spontaneous NETosis and NETosis in response to ANCA stimulation ex vivo, bead phagocytosis, endothelial cell injury, bead phagocytosis and in vitro cell survival 3.Investigate whether spleen tyrosine kinase (SYK) is up-regulated or activated in LDG and determine if ANCA IgG induced responses in LDG are more responsive to treatment with a small molecule SYK inhibitor than in NDG These studies will further our understanding of neutrophil subsets such as LDG and the role they play in pathogenesis of autoimmune and inflammatory diseases such as AAV. The presence of LDG may predict response to treatment or likelihood of relapse. By understanding more about the phenotype of these cells and the role they play in injurious responses in AAV, we may be able to target them directly leading to novel therapeutics with decreased infectious side effects than would be seen with global immunosuppression.

Lay abstract: ANCA associated vasculitis (AAV) is a type of autoimmune disease that occurs when the immune system sees components of our white blood cells as foreign instead of self, and it causes inflammation of the small blood vessels (vasculitis) around the body. The blood vessels in many different organs can be affected by AAV, including the gut, skin, nerves, lung and kidneys, and the condition is often life-threatening. Current treatments for vasculitis may not be effective and are often associated with side effects. By understanding more about what causes this disease we hope to identify new treatments which are more effective and safer. We know that neutrophils (a type of white blood cell) are very important in ANCA associated vasculitis. The autoantibody in AAV can bind to and activate neutrophils, which leads to damage to blood vessels. There is a specific type of neutrophil, LDG, which has been shown to be important in other auto-immune and inflammatory conditions as it is more inflammatory and causes more cell damage than ‘normal’ neutrophils. We have identified these cells in our patients with ANCA associated vasculitis and plan to investigate further the role they play in this condition. If we could target these cells directly, rather than all neutrophils, we may be able to develop more specific treatments with less infectious side effects. We plan experiments to understand how these cells are different from normal neutrophils and how they respond to stimulation with ANCA.

Research activity codes: 1.1 NORMAL BIOLOGICAL DEVELOPMENT AND FUNCTIONING;2.1 BIOLOGICAL AND ENDOGENOUS FACTORS
Health categories: CARDIOVASCULAR