Induction of Passive Heymann Nephritis in Complement Component 6-Deficient PVG Rats

Abstract

Passive Heymann nephritis (PHN), a model of human membranous nephritis, is induced in susceptible rat strains by injection of heterologous antisera to rat renal tubular Ag extract. PHN is currently considered the archetypal complement-dependent form of nephritis, with the proteinuria resulting from sublytic glomerular epithelial cell injury induced by the complement membrane attack complex (MAC) of C5b-9. This study examined whether C6 and MAC are essential to the development of proteinuria in PHN by comparing the effect of injection of anti-Fx1A antisera into PVG rats deficient in C6 (PVG/C6−) and normal PVG rats (PVG/c). PVG/c and PVG/C6− rats developed similar levels of proteinuria at 3, 7, 14, and 28 days following injection of antisera. Isolated whole glomeruli showed similar deposition of rat Ig and C3 staining in PVG/c and PVG/C6− rats. C9 deposition was abundant in PVG/c but was not detected in PVG/C6− glomeruli, indicating C5b-9/MAC had not formed in PVG/C6− rats. There was also no difference in the glomerular cellular infiltrate of T cells and macrophages nor the size of glomerular basement membrane deposits measured on electron micrographs. To examine whether T cells effect injury, rats were depleted of CD8+ T cells which did not affect proteinuria in the early heterologous phase but prevented the increase in proteinuria associated with the later autologous phase. These studies showed proteinuria in PHN occurs without MAC and that other mechanisms, such as immune complex size, early complement components, CD4+ and CD8+ T cells, disrupt glomerular integrity and lead to proteinuria.

Nephrotic Syndrome and Subepithelial Deposits in a Mouse Model of Immune-Mediated Anti-Podocyte Glomerulonephritis

“…Furthermore, depletion of this T cell population prevented proteinuric disease in both models, indicating that T cells are necessary for podocyte injury (18,36). Interestingly, we found increased glomerular T cell numbers as well as monocytes/macrophages and neutrophils in APN mice, as has been reported for PHN (30).…”

“…The observed time course was similar to the autologous and heterologous phases of PHN (18,32). Mice treated with anti-podocyte Ab did not develop elevated serum urea nitrogen or serum creatinine values despite nephrotic syndrome.…”

“…Whereas the presence of infiltrating mononuclear cells is not typical for human membranous glomerulopathy, cytotoxic CD8-positive T cells infiltrating the glomerulus were described in both HN and PHN (18). Furthermore, depletion of this T cell population prevented proteinuric disease in both models, indicating that T cells are necessary for podocyte injury (18,36).…”

“…In PHN, an increase in glomerular, periglomerular, and tubulointerstitial T cell number has been reported (18,30). Therefore, we determined the number of inflammatory cells in the glomerulus and in the periglomerular space by immunostaining with Abs against F4/80 (monocytes/macrophages), MAC-2 (monocytes/macrophages in the glomerulus), CD3 (T cells), and Ly6G (neutrophils) in anti-podocyte and preimmune serumtreated mice at day 14 (Fig.…”

“…Until recently, complement activation and C5b-9 membrane attack complex formation at the podocyte were thought essential to the development of PHN (16,17). However, PHN can be induced in complement 6-deficient rats (PVG C6 2/2 ) that cannot activate the complement cascade to form C5b-9 membrane attack complex (18). The same rats were used to show that HN is not complement dependent (19).…”