FRI0524 HUMAN MONOCLONAL ACPAS INDUCE MOBILITY OF PRIMED SYNOVIAL FIBROBLAST IN A PAD-DEPENDENT PATHWAY

Background Anti-citrullinated protein antibodies (ACPA) play an important role in rheumatoid arthritis (RA) pathogenesis. They recognize a wide number of citrullinated targets and show limited cross-reactivity to acetylated ones(1). Objectives We aimed to investigate the effect of monoclonal ACPAs with different binding patterns on RA synovial tissue derived fibroblasts (SF). Methods Synovial fibroblasts were isolated from synovial tissue of RA patients by enzymatic digestion. ACPA and control monoclonal antibodies (mAbs) were derived from single B cells isolated from RA patients. Two monoclonal ACPA (1325:01B09 and 1325:05C06) showed cross-reactivity to acetylated-targets while four of them (1325:04C03, 1325:07E07, 14CFCT2D09, 14CFCT2H12) did not(1). mAbs were tested in synovial fibroblast migration (Incucyte live time image analysis) and osteoclast formation (TRAP) assays. The role of mAbs cross-reactivity was tested in fibroblast migration assays using inhibitors of peptidylarginine deiminases (Cl-amidine), histone acetyltransferase (anacardic acid) and histone deacetylase (trichostatin A). Binding patterns of monoclonal ACPAs were tested in synovial biopsies obtained from both healthy donors and RA patients. Results One acetylation cross-reactive ACPA (1325:01B09) and two with no cross reactivity (14CFCT2D09 14CFCT2H12) significantly enhanced fibroblast migration (mean±SD fold increase of 1.9±0.5, 1.7±0.4 and 1.8±0.6, respectively) compared to control mAb 1362:01E02 (p Conclusion Monoclonal ACPAs have distinct cellular effects on synovial fibroblasts and osteoclasts that are not related to cross reactivity towards acetylated targets References [1] K. A. Lloyd, G. Wigerblad, P. Sahlstrom, M. G. Garimella, K. Chemin, J. Steen, P. J. Titcombe, B. Marklein, D. Zhou, R. Stalesen, E. Ossipova, C. Lundqvist, O. Ekwall, J. Ronnelid, D. L. Mueller, M. C. I. Karlsson, M. J. Kaplan, K. Skriner, L. Klareskog, F. Wermeling, V. Malmstrom, C. Gronwall, Differential ACPA Binding to Nuclear Antigens Reveals a PAD-Independent Pathway and a Distinct Subset of Acetylation Cross-Reactive Autoantibodies in Rheumatoid Arthritis. Front Immunol9, 3033 (2018). Disclosure of Interests Meng Sun Grant/research support from: Yes, but not for presented project., Akilan Krishnamurthy: None declared, Alexandra Circiumaru: None declared, Marianne Engstrom: None declared, Johanna Steen: None declared, Philip Titcombe: None declared, Vivianne Malmstrom: None declared, Heidi Wahamaa: None declared, Lars Klareskog Grant/research support from: Yes, but not for the presented study., Bence Rethi: None declared, Anca Catrina Grant/research support from: Yes, but not for the presented study.