A10.03 B cell depletion with rituximab in patients with rheumatoid arthritis: Multiplex bead array reveals kinetics ofigg and iga autoantibodies to citrullinated antigens

Background and purpose Seropositivity for Rheumatoid factors and for antibodies to citrullinated (Cit) protein antigens (ACPA) is the strongest predictor for clinical response to Rituximab (rituximab) in rheumatoid arthritis (RA). The aim of this study was to follow fluctuations of IgG- and IgA-ACPA to multiple individual citrullinated protein epitopes in relation to clinical improvement and resumption of symptoms after rituximab. Methods 16 patients with severe, active RA (DAS28 ≥ 5.1) undergoing initial cycles of rituximab were included. All achieved peripheral B-cell depletion ( Results At Baseline, MFI of IgG- and of IgA-Cit antibodies were strongly correlated (R2 = 0.75; p Conclusion Dissection of the ACPA response after rituximab using multiplex bead array revealed diverse kinetics of autoantibody production and followed several distinct patterns, largely un-related to Cit-epitope specificity. At Relapse, rising levels of ACPA with the same specificities as those at baseline suggested re-expansion of residual Cit-specific memory B cells. As B cell return is mandatory for relapse, and with no marked presence of new autoantibody specificities, potential interactions between newly generated and residual B cells could be exploited for more efficient B cell directed therapies.