238. Disease activity and relapse tendency in AAV are reflected by neutrophil and intermediate monocyte frequencies

Background: 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. Methods: 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++ CD16-), non-classical (CD14+ CD16+) and intermediate (CD14++ CD16+). Neutrophils were subdivided into CD16++ or CD16+ as well as CD177+ or CD177-. 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. Results: AAV patients have decreased frequency of eosinophils (p=0,014), increased frequency of CD16+ (p=0,0042), CD16++ (p<0,0001) and CD177 + (p<0,0001) neutrophils and CD14++ CD16+monocytes (p