Spatial arrangement of subepithelial deposits in lupus and nonlupus membranous nephropathy

Subepithelial deposits are a common feature of idiopathic membranous glomer ulonephritis (MGN) and lupus membranous glomerulopathy (LMGN). We investiga ted the spatial arrangement of immunoglobulin G (IgG) and C3c fraction of c omplement (C3c) in the immune deposits of MGN and LMGN with confocal laser scanning microscopy to correlate specific patterns of IgG-C3 interactions w ith different diseases. Ten patients with MGN and 8 patients with LMGN (Wor ld Health Organization class VB) were selected. A determination of the spat ial arrangement of the two fluorochromes and the glomerular area occupied b y each fluorochrome was performed for each case. Our results showed MGN spe cimens have an orderly distribution of IgG and C3c, with each deposit showi ng an outer ring of sole IgG, IgG was always more abundant than C3e (1,619 +/- 271 v 790 +/- 105 mu m(2), P = 0.002), In LMGN, IgG and C3e were haphaz ardly arranged, with deposits made of C3e only and an outer ring of IgG onl y rarely present. Also, the relative amounts of the two antigens were varia ble, and two groups could be identified (group 1: IgG, 5,515 +/- 1,179 mu m (2) v C3c, 4,810 +/- 1,174 mu m(2); P = 0.02; group 2: IgG, 3,358 +/- 658 m u m(2) v C3c, 4,047 +/- 740 mu m(2); P = 0.03). Our data show that diffuse IgG capping of the subepithelial immune deposits is diagnostic of MGN. The absence of an orderly three-dimensional arrangement in LMGN deposits (ie, o uter ring of IgG) is likely to render active complement components more rea dily available to inflammatory activities. (C) 1999 by the National Kidney Foundation, Inc.