POS0333 CIRCULATING NON-CLASSICAL CD14low/-CD16+ MONOCYTES AND THEIR EXPRESSION OF ARGINASE-1 ARE ASSOCIATED WITH THE ACTIVITY OF AXIAL SPONDYLOARTHRITIS

Abstract

BackgroundHuman peripheral blood monocytes represent heterogeneous population and can be divided into three major populations, classical (CD14++CD16−), intermediate (CD14++CD16+) and non-classical (CD14+CD16++) monocytes. All three monocyte populations are thought to have different functional activity, including their pro- and anti-inflammatory activity. The ratio between monocyte populations could change in inflammatory conditions that it is thought to be important for the development of adequate immune responses. Axial spondyloarthritis (axSpA) being autoimmune diseases is currently classified as an autoinflammatory disease based on a strong inflammatory component. It is accepted that increased concentration of pro-inflammatory mediators can cause an impairment of myelopoiesis.ObjectivesThe present study aimed to analyze the frequency of blood monocyte subpopulations and their expression of the suppressor molecule arginase-1 (Arg1) in patients with axSpA.MethodsThe study included 14 healthy donors and 19 axSpA patients aged 23 to 59 years, including 15 men and 4 women. Ankylosing Spondylitis Disease Activity Score (ASDAS) was used to assess disease activity and high activity was determined as ASDAS≥2.1. The disease duration at the time of the study was 12 years (median). Phenotypic analysis of blood monocytes was performed by flow cytometry based on CD14 and CD16 expression.ResultsThe frequency of monocyte subpopulations in patients with low/moderate activity of axSpA did not differ from the donor group. Patients with high/very high disease activity showed an increased relative number of non-classical CD14low/-CD16+ monocytes (vs donors pU=0.007). All donor monocyte subpopulations expressed suppressor intracellular molecule Arg1 with higher expression in intermediate and non-classical monocytes. The expression of Arg1 in CD14low/-CD16+ monocytes was significantly reduced in patients with high activity (vs donors Me 41.5 vs 76.5%, pU=0.01). Patients with the presence of peripheral articular manifestations of axSpA were characterized by a decreased Arg1 expression in non-classical monocytes compared with the donor group (pU=0.02). However, patients without peripheral manifestations demonstrated a significant reduction of Arg1 expression in all monocyte subpopulations (pU<0.05).ConclusionShifting of monocyte subpopulation toward a higher number of non-classical monocytes with the decrease in the expression of the suppressor molecule Arg1 in the high activity of axSpA can play important role in terms of the possible involvement of monocytes in maintaining inflammation and its regulation in autoinflammatory disease.The reported study was funded by State Budgeted Project (registration ID 122011800324-4, 122011800108-0, 122012000373-3).Disclosure of InterestsNone declared