The Anti-mutated Citrullinated Vimentin Response Classifies Patients with Rheumatoid Arthritis into Broad and Narrow Responders

Objective. Autoantibodies against citrullinated peptide antigens (ACPA) are routinely determined to diagnose rheumatoid arthritis (RA) and are predictive of a more severe course of the disease. We here set out to address an involvement of ACPA in the pathogenesis of RA and investigated the recognition pattern of antibodies against 2 citrullinated antigens in more detail. Methods. The sera of 77 patients fulfilling the American College of Rheumatology criteria for RA were analyzed for subclass titers of anti-mutated citrullinated vimentin (MCV) and anticyclic citrullinated peptide (CCP) antibodies by combining subclass specific detection antibodies with commercially available CCP and MCV ELISA plates. Cross-reactivities between anti-MCV and anti-CCP antibodies were detected using a sequential ELISA system. Results. IgG1, IgG3, and IgG4 titers among anti-MCV and anti-CCP antibodies correlated significantly. Cross-reactivity of MCV-specific antibodies against CCP could be detected in 8 of 16 patients’ sera; however, cross-binding of MCV-specific IgG4 was weaker compared to total IgG. Conclusion. The inherent capacity of IgG4 to exchange F(ab) arms provides insight into the anti-MCV antibody diversity and suggests a classification of ACPA positive patients into broad and narrow responders.