Glomerular IgA ₁ and IgA ₂ Deposits in IgA Nephropathies

Abstract

IgA<sub>1</sub> and IgA<sub>2</sub> deposits in the renal glomeruli were studied in 29 biopsy specimens from 17 children with IgA nephropathy and 12 children with anaphylactoid purpura nephritis. IgA<sub>1</sub> and IgA<sub>2</sub> were detected with the indirect immunofluorescence method, using various combinations of dilutions of sheep antihuman IgA subclass antisera and fluorescein isothiocyanate conjugated rabbit antisheep IgG antiserum. The glomeruli of all the 29 specimens studied were strongly positive for IgA<sub>1</sub>, while only twelve specimens were positive for IgA<sub>2</sub>. Ten specimens without IgM deposits were all negative for J chain. These results indicate that the glomerular IgA deposits consist mainly of monomeric IgA<sub>1</sub>, with a minor share for IgA<sub>2</sub>. The serum IgA in normal individuals consists of about 90% IgA<sub>1</sub> and 10% IgA<sub>2</sub>. Therefore, it was assumed that the serum IgA is deposited irrespective of subclass in the glomeruli of the patients with IgA nephropathies.