Anti-myeloperoxidase associated glomerulonephritis: a study of innate immune activation

ANCA-associated vasculitis (AAV) is characterised by macrophage and neutrophil infiltration at the site of injury. Animal models have been used to study the disease and to try different treatment approaches. The aim of this study was to investigate the involvement of the innate immune system in AAV. This was done by looking at different innate immune system components such as macrophages and neutrophils. There were a large number of CD68+ cells in the crescent region of the kidney following treatment with anti-MPO antibodies and LPS. Serial section staining has shown that these cells are more likely to be classically activated macrophages. Furthermore, gene expression studies have confirmed the up regulation of genes associated with classically activated macrophages such as calprotectin. In addition, there was an up regulation of genes associated with macrophages accumulation such as CCR2 and CX3CR1. These macrophages could be involved in secreting TGF-β, which was up regulated, which can lead to an increase in extracellular matrix such as collagen. Blocking macrophage accumulation was evaluated using anti-mouse CCR2 which was effective in depleting GR1+ blood monocytes. However, there was no significant difference on the disease outcome following treatment with anti-mouse CCR2. This suggests a lesser role of macrophages in the development of vasculitis or that disease was mild and so an effect could not be identified. In addition, I investigated the variability in ANCA-induced neutrophil degranulation from healthy donors. I purified human neutrophils from healthy donors and treated them with different ANCA IgG samples. I found that these neutrophils responded differently to the same ANCA IgG as measured by neutrophil degranulation using ELISA. I tried to study the resulting metabolites using mass spectrometry but there was a considerable degree of technical variation which prevented making final conclusions. However, this was a novel approach and provided me with good ideas on how to take it further. I also looked at the III effect of pre-treating neutrophils with simvastatin. I found a significant reduction in ANCA-induced neutrophil degranulation following treatment with a statin. In conclusion, preventing macrophage infiltration did not have an effect on the development of the disease in mice. This could be because the disease was mild or because resident macrophages are more important than infiltrating ones. In addition, the microarray experiment has provided interesting results that could be used to find common pathways in mouse, rat and human. It also provided more information on genes that are upregulated in the kidney following AAV induction. This could be used to arrange the genes into pathways and biological processes to study the involvement of macrophages and other components of the innate immune system. Finally, simvastatin significantly reduced ANCA-induced neutrophil degranulation