Charge distribution of plasma IgG and IgG immune complexes in IgA nephropathy

IgA nephropathy is characterized by a predominant deposition of IgA in the glomerular mesangium. However, in many cases, deposition of IgG also occurs and the concentration of circulating IgG immune complexes is higher than that in controls. To examine further the possible role of the charge of immunoglobulins in the pathogenesis of IgA nephropathy, we used isoelectric focusing (IEF) and densitometry to investigate the charge distribution of plasma IgG and IgG immune complexes in patients with this disease. Blood samples were taken from patients and healthy adults, and plasma and samples treated with 7.0% polyethylene glycol (PEG) were used. All samples were focused with a Multiphor II flatbet electrofocusing unit apparatus on an agarose gel, then immunofixed with polyclonal goat anti-human IgG, and stained with Coomassie blue R 250. The stained gels were analyzed by densitometry. 1. In plasma, the areas of PI 10-8.9 and PI 10-8.6 in IgA nephropathy were higher in the patients than in the controls. 2. In the 7.0% PEG precipitation, the area PI 8.1-6.1 was higher in the patients than in the controls. These findings suggest that a change in charge distribution of IgG and IgG immune complexes may contribute to the pathogenesis of IgA nephropathy.