== Peripheral blood was collected from healthy control individuals, AAV patients (both patients with active disease and those in remission), and patients with other renal disease (disease controls)

== Peripheral blood was collected from healthy control individuals, AAV patients (both patients with active disease and those in remission), and patients with other renal disease (disease controls). differently to antibodies directed against MPO and PR3, with anti-MPO but not anti-PR3 leading to increased IL-1, IL-6 and IL-8 production. In concordance Norepinephrine with the observed higher surface expression of MPO on intermediate monocytes, this subset produces the highest quantity of IL-1 in Norepinephrine response to anti-MPO activation. These data suggest that monocytes, specifically, the intermediate subset, may play a role in ANCA vasculitis, and also show that substantial differences exist between the effect of anti-MPO and anti-PR3 antibodies on these cells. Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) refers SETD2 to a group of severe multi system autoimmune diseases affecting the microvasculature1. This encompasses microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA, formally known as Wegners granulomatosis) and Norepinephrine eosinophilic granulomatosis with polyangiitis (EGPA, formerly known as Churg-Strauss syndrome). In most cases AAV is usually characterised by autoantibodies to myeloperoxidase (MPO) or proteinase-3 (PR3)2,3. These proteins are primarily found in the cytoplasmic granules of neutrophils and lysosomes of monocytes. Substantial clinical and experimental evidence indicates that these autoantibodies drive pathogenesis of the disease4,5. GPA, EGPA and MPA share the same pathology of necrotising vasculitis of small vessels, the primary difference between them being the development of granuloma in EGPA and GPA but not MPA, with marked eosinophilia and asthma in EGPA. The majority of AAV research to date has focused on the neutrophil as the dominant cell driving pathology, with the role of the monocyte being less well examined. However, much like neutrophils, monocytes also express the antigenic targets MPO and PR3 and macrophages are frequently found in the vascular infiltrates of both kidneys and lungs of patients with AAV6. In addition, ANCA have been shown to induce the production of oxygen radicals7and interleukin (IL)-88in monocytes. For many years monocytes were classified into 2 subsets based on their expression of the Fc gamma III receptor, CD16 (CD16- and CD16+ monocytes). Recently, the CD16+ subset has been subdivided based on their surface expression of the lipopolysaccharide (LPS) co-receptor, CD14, resulting in 3 unique monocyte populations (Table 19): classical (CD14highCD16neg/low), intermediate (CD14highCD16high) and non-classical (CD14lowCD16high). Classical monocytes comprise the largest subset and appear to have a role in proinflammatory responses as well as having antimicrobial effects. The previous functions described for CD16+ monocytes have yet to be fully attributed to either the intermediate or non-classical subtype, but intermediate monocytes appear to have a proinflammatory role while the non-classical subset have a patrolling and anti-viral function. ANCA activation of neutrophils has been shown to require the Fc portion of the autoantibody for full effect10, suggesting that ANCA may interact with CD16 on monocytes and therefore, unique monocyte subsets may play a key role in the pathogenesis of the disease. Differences in the proportion of monocyte subsets, particularly an increase in intermediate cells, has previously been shown in a number of autoimmune diseases including rheumatoid arthritis11, sarcoidosis12, and severe asthma13. We therefore postulated that unique monocyte subsets may exhibit different responses to the autoantibodies associated with ANCA vasculitis. == Table 1. Monocyte subset markers and phenotype (adapted from32). == % in peripheral blood refers to the median and interquartile range (IQR) of all samples included in this study. == Results == == The proportion of intermediate monocytes is usually increased in AAV patients == Monocyte subsets were analysed in AAV patients (n = 100, 19 active and 81 remission), disease control patients (n = 18) and healthy control individuals (n = 44) (Table 2). Individual subsets were recognized Norepinephrine based on cell surface expression of CD14 and CD16 as measured by flow cytometry. We observed no significant difference in the proportion of classical and non-classical monocytes, as a percentage of total monocytes, between healthy controls, disease controls and AAV patients (remission or active) (Fig. 1A,C). Intermediate monocytes were significantly increased in both remission and active AAV patients when compared.