Measurement of Serum IgG4 Levels by an Established ELISA System and Its Clinical Applications in Autoimmune Diseases

摘要

IgG4-related disease (IgG4-RD) is a novel and rare autoimmune disease entity.Elevated serum IgG4 level is strongly suggestive of IgG4-RD.But it is still unknown whether serum IgG4 elevation commonly occurs in other autoimmune diseases.In this study,the serum IgG4 levels were detected by an established enzyme-linked immunosorbent assay (ELISA) in a variety of autoimmune diseases including systemic lupus erythematosus (SLE),Sjogren's syndrome (SS),polymyositis or dermatomyositis (PM/DM) and IgG4-RD.To evaluate the reliability of this ELISA system,some of our samples were sent to a lab in Kanazawa Medical University,Japan,and detected by using the nephelometric assay.The results showed that our findings were consistent with theirs.Moreover,it was found that the serum IgG4 levels were 0.23±0.16 g/L in 53 healthy controls,0.16±0.15 g/L in 103 SLE patients,0.22±0.18 g/L in 41 SS patients and 0.40±0.32 g/L in 21 PM/DM patients.No significant difference in the serum IgG4 level was observed among these groups (P>0.05).The serum IgG4 levels of two cases of IgG4-RD were 1.63 and 4.65 g/L respectively,and both decreased markedly after treatment with glucocorticoids.These data indicated that this established ELISA system can be used for detecting serum IgG4 levels.Elevated serum IgG4 levels help diagnose IgG4-RD and evaluate the curative effect of this condition rather than other autoimmune diseases.