Serum immunoglobulins and IgG subclasses in patients with glomerulonephritis.

The serum concentrations of IgG, IgA, IgM and of the four subclasses of IgG were determined by radial immunodiffusion in 103 patients, mean age 42 (range 16-72), with various types of glomerulonephritis. Forty-nine healthy blood donors, mean age 41 years (range 19-65), served as controls. Kidney biopsies were obtained from all the patients for examination by histopathology and by immunofluorescence. The glomerulopathies were classified according to WHO criteria. The serum immunoglobulin patterns were different for the various clinical groups of patients. Patients with Wegener's granulomatosis, rapidly progressive glomerulonephritis and SLE had a significant increase in total IgG and of IgG4 (P less than 0.05-0.001). Patients with minimal change disease had low concentrations of IgG (P less than 0.001) with a significant decrease in IgG1 and IgG2 (P less than 0.001 and 0.01, respectively). Highly significant increases in IgA were noted for patients with IgA nephritis (P less than 0.001) but high levels were also seen in patients with chronic glomerulonephritis. The findings might have diagnostic implications.