IgA-associated glomerulonephritides: A study with monoclonal antibodies

Thirty-six renal biopsies from patients with various glomerulonephritides which exhibited prominent IgA deposits were studied by indirect immunofluorescence technique utilizing monoclonal antibodies specific for α chain (IgA), IgA1 and IgA2 subclasses, secretory IgA, and secretory component. The ability of the IgA deposits to bind free secretory component in vitro was examined in five biopsies of IgA nephropathy of Berger and in five biopsies of lupus nephritis. All the biopsies revealed IgA1 deposits. Associated IgA2 was found in lupus nephritides and hepatic glomerulopathy. Secretory IgA and free secretory component were not detected in any biopsy. In situ free secretory component binding was demonstrated in IgA nephropathy of Berger but not in lupus nephritides. These results indicate that polymeric IgA1 molecules are the chief nephritogenic antibodies in IgA nephropathy of Berger, that there is a high frequency of association of IgA1 and IgA2 in lupus nephritides and, perhaps, hepatic glomerulopathy, and that secretory IgA does not appear to play a role in IgA-associated glomerulonephritis.