Immunoglobulin G and immunoglobulin A anti-Ro52 in plasma and saliva show little association with disease activity in patients with primary Sjögren’s disease

OBJECTIVE: Primary Sjögren's disease (pSjD) is one of the most common autoimmune connective tissue diseases. Sicca symptoms are a hallmark of pSjD. Up to 80% of patients have immunoglobulin G (IgG) anti-Ro52 autoantibodies in their plasma. This study investigates the frequency of IgG and IgA anti-Ro52 autoantibodies in plasma and saliva from pSjD patients, and assess the associations between disease activity and autoantibody titers. METHOD: The study was conducted on a Norwegian cross-sectional SjD cohort (n = 113). IgA and IgG anti-Ro52 autoantibodies were measured in plasma and saliva by an indirect in-house enzyme-linked immunosorbent assay (ELISA). ELISA results were correlated with clinical data using relative risk and Spearman's correlation coefficients. RESULTS: Measuring plasma, 73% of the cohort were positive for IgG anti-Ro52 and 47% for IgA anti-Ro52 autoantibodies. In saliva, 34% were positive for IgA anti-Ro52 and 17% for IgG anti-Ro52 autoantibodies. We observed an inverse correlation between plasma IgG anti-Ro52 autoantibodies and disease activity. Patients with a low plasma titre of IgG anti-Ro52 autoantibodies had a higher probability of reporting pain, as indicated by the EULAR Sjögren's Syndrome Patient Reported Index score (relative risk = 0.48, 95% confidence interval 0.29-0.80, p = 0.002). Furthermore, plasma IgA anti-Ro52 correlated significantly with the focus score. CONCLUSION: IgA and IgG anti-Ro52 autoantibodies in saliva and plasma showed an inverse correlation with disease activity but significant positive association with immune activity in patients with SjD. Our findings do not support the use of salivary IgA and IgG anti-Ro52 autoantibodies as biomarkers of disease activity in SjD.