Anti-agalactosyl IgG antibodies in sera from patients with systemic sclerosis

Objective. To determine the prevalence and clinical correlations of anti-agalactosyl IgG antibodies (anti-AG IgG) in patients with systemic sclerosis (SSc). Methods. Serum samples from patients with limited cutaneous SSc (ISSc; n = 49), diffuse cutaneous SSc (dSSc; n = 21), rheumatoid arthritis (RA; n = 10), systemic lupus erythematosus (SLE; n = 20), and healthy individuals (n = 20) were examined by lectin-enzyme immunoassay using human agalactosyl IgG as antigen. Results. Anti-AG IgG were detected in 52 (74%) of 70 patients with SSc, which was much higher than the frequency of rheumatoid factor positivity in SSc (16%). Levels of anti-agalactosyl IgG antibodies were significantly higher than in healthy controls or patients with SLE, but lower than patients with RA. Levels of anti-AG IgG in patients with dSSc were significantly higher than in ISSc. SSc patients with anti-topoisomerase I antibodies had significantly higher levels of anti-AG IgG than SSc patients with anticentromere antibodies. Concerning clinical correlation, patients with pulmonary fibrosis showed elevated levels of anti-AG IgG compared to those without pulmonary fibrosis. Patients with decreased %VC or %DLCO showed increased levels of anti-AG IgG. Elevated levels of anti-AG IgG were associated with the presence of contracture of phalanges or cutaneous calcinosis, but not the presence of arthritis/arthralgia. Conclusion. The results suggest that anti-agalactosyl IgG antibody is frequently detected in SSc and is a serological indicator for more severe SSc.