Given the important role of ACPA as a diagnostic and prognostic biomarker for RA40, ACPA Fab glycosylation as a potential predictive marker for the transition from symptom-free autoimmunity to autoimmune disease22 and the increasing awareness of Fab glycosylation also in other autoantibody species41, the approach introduced here has high potential to further our understanding of autoantibody responses not only in RA, but also in autoantibody-characterized autoimmune diseases in general. This evidence concerns the gene PRTN3 and rheumatoid arthritis.