CD79A and rheumatoid arthritis: Preclinical RA has been characterized by circulating IgA and IgG classes of autoantibodies targeting citrullinated protein antigens (ACPAs) that are highly specific for future clinical RA, circulating IgA plasmablasts, and autoantibody production at mucosal sites, all of which point toward mucosal tissues as the origin of immune dysregulation.