Long-term Ro60 humoral autoimmunity in primary Sjِgrenʹs syndrome is maintained by rapid clonal turnover

Long-term humoral autoimmunity to RNA–protein autoantigens is considered a hallmark of systemic autoimmune diseases. We use high resolution Orbitrap mass spectrometric autoantibody sequencing to track the evolution of a Ro60-specific public clonotypic autoantibody in 4 patients with primary Sjögrenʹs syndrome. This clonotype is specified by a VH3–23/VK3–20 heavy and light chain pairing. Despite apparent stability by conventional immunoassay, analysis of V-region molecular signatures of clonotypes purified from serum samples collected retrospectively over 7 years revealed sequential clonal replacement. Prospective longitudinal studies confirmed clonotype loss and replacement at approximately three-monthly intervals. Levels of secreted anti-Ro60 clonotypes fluctuated markedly over time, despite minimal changes in clonal affinity. Our novel findings indicate a relentless turnover of short-lived clonotypic variants, masquerading as long-lived Ro60 humoral autoimmunity.