Measuring decreased serum IgG sialylation: a novel clinical biomarker of lupus

Introduction The aim of this work was to develop a simple assay to distinguish between patients with rheumatoid arthritis (RA) and patients with systemic lupus erythematosus (SLE) by measuring the serum sialylated IgG (SAIgG). Methods Using a newly established SNA-based ELISA method, we compared the sialylation of immunoglobulin G (IgG) from a healthy control group (n=41), RA patients (n=30), SLE patients (n=45), patients with neuropsychiatric SLE (NPSLE) (n=30) and patients with juvenile idiopathic arthritis (JIA) (n=32). Results The average SAIgG level in healthy control individuals, RA patients, JIA patients, SLE patients and NPSLE patients was 0.640.17, 0.82 +/- 0.33, 0.69 +/- 0.23, 0.12 +/- 0.02 and 0.03 +/- 0.01mg/ml, respectively. The ratio of sialylated IgG to total IgG was significantly decreased in the SLE group (1.88 +/- 0.32%) compared with the healthy population (4.64 +/- 0.90%). Conclusion In summary, while the mean serum SAIgG level of RA and JIA patients was similar to that of the healthy population, there was a significant decrease in the serum SAIgG of both SLE groups tested, whereby the level of the NPSLE population group was the lowest.