Double immunofluorescence studies of IgA and poly C9 (MAC) in glomeruli from patients with IgA nephropathy

Double immunofluorescent studies on IgA, poly (MAC) or C3 in glomeruli from patients with IgA nephropathy are described. Renal biopsy specimens were obtained from 12 patients with IgA nephropathy, four patients with proliferative glomerulonephritis (PGN) and two normal human kidney (NHK). These specimens were incubated with monoclonal anti-poly C9 (membrane attack complex; MAC) and then stained with FITC-labelled goat anti-mouse immunoglobulin (Ig) antiserum. After washing with phosphate buffered saline (PBS) (pH 7.4), the sections were stained with rhodamine-labelled rabbit anti-human IgA antiserum and examined by fluorescence microscopy. The sections were also stained with FITC-labelled goat anti-human C3 antiserum and then stained with rhodamine-labelled rabbit anti-human IgA antiserum. Markedly combined depositions of IgA and poly C9 or C3 in glomeruli were observed in patients with IgA nephropathy. There was a significant correlation between the deposition of poly C9 and the grading of histopathological injuries in such patients. There was also a significant correlation between the deposition of poly C9 in the extraglomerular vascular vessels and the ageing in patients with IgA nephropathy, PGN and NHK. It appears that the deposition of poly C9 might detect directly the activities of complement in glomeruli from patients with IgA nephropathy.