A study on the detection of
polymeric IgA in glomeruli from renal biopsy specimens in patients with
IgA nephropathy is described. Renal biopsy specimens were obtained from patients with
IgA nephropathy. These specimens were stained with
FITC-labelled anti-human J chain
antisera and then examined with a fluorescent microscope. The J chain was observed in the glomerular mesangium by immunofluorescent staining. In parallel studies, renal biopsy specimens were treated with
citrate buffer (pH 3.2) and the 'eluate' was neutralized by
sodium hydroxide. The eluate was labelled with
iodine-125, and the radiolabelled 'eluate' was fractionated by
sucrose density-gradient ultracentrifugation. Polymerized
IgA in the 'eluate' obtained from patients with
IgA nephropathy was found to sediment predominantly as 9S to 11S using a
sucrose density gradient analysis.
Polymeric IgA in the fractions of the density gradient analysis was determined by anti-human
IgA and anti-human J chain
antisera. It was demonstrated that
IgA and J chain were eluted from the glomeruli in some patients with
IgA nephropathy. It is concluded that
IgA deposited in the glomeruli is composed of dimers and/or larger
polymers of circulating
IgA in some patients with
IgA nephropathy.