A study of the relationship between IgG subclass/IgM and idiopathic nephrotic syndrome

In an attempt to elucidate the relationship between serum IgG subclass/IgM ratio and prognosis in different types of idiopathic nephrotic syndrome (INS), 46 cases of treatment responders and 23 cases of either frequent relapse or non-responders were studied. All patients had received renal biopsy. Serum IgG subclass/IgM ratios were compared between the acute nephrotic phase and remission. The association between therapeutic effect and the parameters of INS were also investigated. There were 24 cases of minimal change nephrotic syndrome (MCNS), 32 cases of IgM nephropathy (IgMN) and 13 cases of focal segmental glomerular sclerosis (FSGS). All cases of MCNS were steroid-responders. Seventeen cases of IgMN experienced frequent relapses. The other 15 cases were responsive to the treatment. 6 cases of FSGS had poor response to any therapy; 7 cases were responsive to either triple therapy or cyclosporine A plus prednisolone. Both IgGI/IgM and IgG2/IgM were correlated with serum albumin and cholesterol levels at the acute nephrotic phase (p < 0.05). Longitudinal change of the immunologic parameters in patients with INS revealed significantly elevated serum IgM level decreased serum IgG level, IgG/IgM, IgG1/IgM, IgG2/IgM, IgG3/IgM, IgG4/IgM and IgG/IgE ratio during acute nephrotic phase. Correlation between therapy responses showed that, for serum IgG1/IgM ratio > 3.0, most of the cases were treatment-responders. For IgG1/IgM ratio > 1.0, all the cases were frequent relapsers or non-responders. These results suggest the immunologic changes in patients of INS may be caused by immune regulatory abnormality. Serum IgG1/IgM ratio may serve as one of the therapeutic and prognostic guides, especially if the patient refuses renal biopsy.