Elevation of serum IgG subclass concentration in patients with rheumatoid arthritis.

A new concept of IgG subclass such as IgG4-related systemic disease including autoimmune pancreatitis, characterized by a high-serum IgG4 level, has been proposed. Our aim was to investigate serum IgG subclass levels in rheumatoid arthritis (RA). IgG subclass levels of sera from 72 patients with rheumatoid arthritis were determined by immunonephelometric assay. The patients were divided into two groups according to clinical activity of the disease: active disease and remission. The sera from 45 normal controls were also measured. All statistical analyses were carried out with SPSS software version 13.0. We found a significant increase of all the four IgG subclass concentrations in sera of patients with RA compared to those of the controls (P < 0.001). When the patients were divided according to clinical activity, the IgG subclass concentrations were similar between the two groups (P > 0.05). Our data suggest that besides IgG1, IgG2 and IgG3, IgG4 may involve in the pathogenesis of the disease.