238. Disease activity and relapse tendency in AAV are reflected by neutrophil and intermediate monocyte frequencies
Creators: name: Sofia Smargianaki1, 2
name: Evelina Elmér1, 2
name: Lilliebladh3, Sandra
name: Ohlsson3, Sophie
name: Pettersson3, Åsa
name: Hellmark3, Thomas
name: Åsa CM Johansson1, 4
Publisher: name: Zenodo
Year: 2022

description: <strong>Background:</strong> Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of severe autoimmune conditions involving inflammation of the small-sized blood vessels and includes granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). In this study we investigate the relation between different granulocyte and monocyte subtypes and tendency to relapse in AAV patients. <strong>Methods:</strong> Peripheral blood from 105 GPA and MPA patients were collected between year 2011 and 2020 and compared to 126 healthy blood donors (HBD). Circulating eosinophils, basophils, neutrophils and monocytes were analyzed using immuno-phenotyping by multicolor flow cytometry. Monocytes were subdivided into classical (CD14<sup>++ </sup>CD16<sup>-</sup>), non-classical (CD14<sup>+ </sup>CD16<sup>+</sup>) and intermediate (CD14<sup>++ </sup>CD16<sup>+</sup>). Neutrophils were subdivided into CD16<sup>++</sup> or CD16<sup>+</sup> as well as CD177<sup>+</sup> or CD177<sup>-</sup>. Clinical and laboratory data were collected for all patients, including disease activity defined by Birmingham Vasculitis Activity Score 3 (BVAS3), tendency to relapse information and current treatment. <strong>Results:</strong> AAV patients have decreased frequency of eosinophils <em>(p=0,014)</em>, increased frequency of CD16<sup>+ </sup><em>(p=0,0042), </em>CD16<sup>++</sup> <em>(p&lt;0,0001)</em> and CD177 <sup>+</sup> <em>(p&lt;0,0001</em>) neutrophils and CD14<sup>++ </sup>CD16<sup>+</sup>monocytes <em>(p&lt;0,0001) </em>compared to HBD<em>.</em> Paired data from 23 patients showed lower frequency of CD14<sup>++</sup>CD16<sup>+ </sup>monocytes and higher concentration (10<sup>9 </sup>/L) of CD16<sup>++ </sup>neutrophils during active disease. AAV patients with tendency to relapse (Ttr) had higher frequency of CD16<sup>++</sup> and CD177<sup>+</sup> neutrophils (<em>p=0,017 and p=0,028, respectively</em>) compared to non-relapsing AAV patients. Sub-analysis of patients based on diagnosis, showed that different subtypes of neutrophils were increased in GPA patients with Ttr whereas CD14<sup>++</sup>CD16<sup>+</sup> monocytes were decreased in MPA patients with Ttr. AAV patients treated with Rituximab during the past twelve months had higher CD14<sup>++</sup>CD16<sup>+ </sup>(<em>p=0,027)</em> and CD14<sup>++</sup>CD16<sup>-</sup> <em>(p=0,026) </em>monocytes subpopulations. <strong>Conclusions:</strong> We detect a skewing of different granulocyte as well as monocyte subpopulations in patients with AAV that seems to be associated with disease activity and tendency to relapse. Moreover, patients on rituximab treatment showed increased frequency of classical and intermediate monocytes. These findings might be used as biomarkers and for relapse prediction. <strong>Disclosures</strong><strong>: None</strong>