Proteinuria In Heymann Nephritis Research Articles

Nephrin and podocin dissociate at the onset of proteinuria in experimental membranous nephropathy

The slit diaphragm plays a critical role in maintaining the barrier function of the glomerular capillary wall. The pathogenic mechanism of proteinuria in membranous nephropathy remains uncertain. This study was undertaken to analyze the pathogenic role of slit diaphragm in proteinuria in experimental membranous nephropathy. The expression and the localization of slit diaphragm-associated molecules (nephrin, podocin, and CD2AP) and other podocyte-associated molecules (podocalyxin and alpha(3) integrin) in passive and active Heymann nephritis were analyzed by immunofluorescence and Western blot analysis. The interaction of slit diaphragm-associated molecules was investigated by the dual-labeling immunofluorescence method. The mRNA expression of these molecules was also analyzed. Shifts in nephrin and podocin staining patterns, from linear to granular, were detected in the early stages of passive Heymann nephritis. These shifts were not parallel, and the dissociation of these molecules was detected by the dual-labeling immunofluorescence method in passive and active Heymann nephritis. Western blot analyses with sequentially solubilized materials indicated that the nephrin-rich fraction changed from being partly detergent-resistant to being predominantly detergent-soluble. This change did not occur with podocin. Nephrin excreted into urine was already detected in the early stages of passive Heymann nephritis. Decreased mRNA expression of nephrin and podocin was observed before the onset of proteinuria. By contrast, no extensive change in the expression of alpha(3) integrin was observed in this study. Nephrin is dissociated from podocin and excreted into urine in the early stages of Heymann nephritis. The reduced expression of nephrin and podocin, along with their dissociation, may contribute to the development of proteinuria in Heymann nephritis.

Il-4 therapy prevents the development of proteinuria in active Heymann nephritis by inhibition of Tc1 cells.

The role of IL-4, a key Th2 cytokine, in promoting or inhibiting active Heymann nephritis (HN) was examined. HN is induced by immunization with Fx1A in CFA, and proteinuria in HN is associated with subepithelial IgG and C3 deposition and infiltration of CD8(+) T-cytotoxic 1 (Tc1) cells and macrophages into glomeruli, as well as induction of Abs to Crry. Treatment with rIL-4 from the time of Fx1A/CFA immunization stimulated an earlier IgG1 response to Fx1A, induced anti-Crry Abs, and up-regulated IL-4 mRNA in lymphoid tissue, but did not alter proteinuria. Treatment with MRCOx-81, an IL-4-blocking mAb, resulted in greater proteinuria, which suggests endogenous IL-4 regulated the autoimmune response. Delay of rIL-4 treatment until 4 wk post-Fx1A/CFA immunization and just before the onset of proteinuria prevented the development of proteinuria and reduced Tc1 cell infiltrate in glomeruli. Delayed treatment with IL-4 had no effect on titer or isotype of Abs to Fx1A or on Ig, C3, and C9 accumulation in glomeruli. Treatment with rIL-13, a cytokine that alters macrophage function such as rIL-4, but has no direct effect on T or B cell function, reduced glomerular macrophage infiltrate, but did not prevent proteinuria or CD8+ T cell infiltrate. Anti-Crry Abs were paradoxically only induced with rIL-4 therapy, not in HN controls with proteinuria. It was concluded that the rIL-4 effect was probably by inhibition of Tc1 cells, which normally mediate the glomerular injury that results in proteinuria.

Molecular development of immune deposits and proteinuria in Heymann nephritis.

Molecular development of immune deposits and proteinuria in Heymann nephritis.

The role of T cells in the mediation of glomerular injury in Heymann's nephritis in the rat.

Heymann's nephritis (HN), a rat model of the membranous glomerulonephritis in man, is thought to be mediated by auto-Ig with subsequent activation of C. Whether T cell mechanisms are involved in the mediation of HN, apart from CD4+ cells providing help for auto-Ig production, was examined by treatment with mAb specific for T cell subsets for 6 weeks after immunization to induce HN. Anti-CD4 mAb therapy totally prevented proteinuria, in that at 6, 8, and 12 week treated rats had less than 15 mg/day of protein compared to controls that all had greater than 260 mg/day. Ig and C deposition in the glomerulus was significantly less and auto-Ig titers in serum were partially suppressed by anti-CD4 therapy. Anti-CD8 mAb therapy markedly reduced proteinuria at all time points, for example at 6 weeks there was 51 +/- 40 mg/day compared to 183 +/- 120 mg/day (P = 0.0003), but had no effect on auto-Ig titers or on Ig and C deposition in the glomerulus. A non-specific effect of high dose mouse mAb therapy was excluded by the findings that a mAb that did not bind to rat cells had no effect on the induction of HN and that serum C was not depleted in any of the mAb treated animals. A role for T effector mechanisms was further supported by the finding that therapy with mAb to T cell receptor alpha/beta chain or with cyclosporine also markedly delayed the onset of proteinuria. Examination of renal biopsies showed a T cell infiltrate in glomeruli and the interstitium of the untreated HN controls that was not present in MRC Ox35 or MRC Ox8 treated groups. This infiltrate included CD4+ and CD8+ T cells and macrophages. These results suggest induction of proteinuria in HN was totally dependent upon CD4+ T cells, and that CD4+ and CD8+ cells may have a direct role in the mediation of glomerular dysfunction in HN.