IgG subclass serum levels in systemic lupus erythematosus patients.

IgG subclass levels of sera from 105 patients with systemic lupus erythematosus (SLE) were determined by immunonephelometric assay. Patients were divided into two groups according to clinical activity of the disease: active disease and remission. Forty-five normal controls were also measured. We found a significant increase of IgG1 (p = 0.000), IgG2 (p = 0.000), and IgG3 (p = 0.000) in SLE sera, while IgG4 (p = 0.494) values did not differ significantly from those of controls. When patients were divided according to clinical activity, decrease of IgG3 concentration was observed in the patients in remission. In contrast, the concentrations of IgG1, IgG2, and IgG4 subclass were similar between the two groups (p > 0.05). Our data suggest that differential increase of IgG subclasses during the course of SLE may be of relevance to the pathogenesis of the disease.