Objective: It was reported that major subclasses of anti-glomerular basement membrane (GBM) antibody were IgG1 and IgG4. The IgG1 subclass was mainly found in male patients and IgG4 subclass in female patients with anti-GBM disease. This study investigates the distribution of anti-GBM IgG subclasses and their association with clinical characteristics.
Methods: Sera from 50 patients diagnosed as anti-GBM disease during 1991-2003 were collected. The anti-GBM antibodies with IgG1, IgG2, IgG3, and IgG4 subclasses were detected with purified bovine alpha (IV) NC1 as solid phase ligand in ELISA. The association with clinical manifestations was further investigated.
Results: The positive rates of IgG anti-GBM subclasses were IgG1 94%, IgG2 56%, IgG3 12%, IgG4 88%, respectively. IgG1 and IgG4 were the main subclasses in anti-GBM IgG subclasses (P<0.01). The positive rates of the four subclasses had no significant difference between male and female, whereas the average positive percentage of IgG4 anti-GBM antibody was much higher in males than that in females (P<0.01). The average ages of patients with each subclass had no difference. The distribution of anti-GBM subclasses had no association with antineutrophil cytoplasmic antibody (ANCA), hematuria, proteinuria,or hemoptysis. The average positive percentage of IgG1 in patients with serum creatinine over 600 micromol/L was significantly higher than that in patients with serum creatinine less than 600 micromol/L (P<0.05), which suggested IgG1 might play an important role in the evolution and development of the disease. In the four patients with mild clinical presentations, three had IgG4 subclass, and only one patient who retained normal renal function in the follow-up exhibited pure IgG4 subclass. This suggested that IgG4 might not be inclined to cause severe damage. The average positive percentage of IgG4 subclass was higher in smoking patients than that in non-smoking patients (P<0.01).
Conclusion: There is a restrictive distribution among the subclasses of anti-GBM antibody, in which IgG1 and IgG4 are the main subclasses. The distribution of anti-GBM IgG subclasses was not associated with gender.