Engelmann R, et al. - Authors aimed to assess the value of antibodies against citrullinated peptide antigens (ACPA) IgG subclasses and peripheral blood antigen-presenting cells as biomarkers to monitor and predict therapy response of subjects having rheumatoid arthritis (RA). A significant decrease in IgG4 ACPA levels was demonstrated by the responders three months after the therapy began, and this was independent of the individual treatment regimen. A significant increase in CD1c⁺ classical dendritic cells (cDC) was demonstrated by the non-responders. Overall, IgG4 ACPA levels were suggested as biomarkers for monitoring therapy response in RA.