John Reynolds

Experimental autoimmune glomerulonephritis (EAG) can be induced in Wistar-Kyoto (WKY) rats by immunization with the recombinant NC1 domain of the alpha 3 chain of type IV collagen [α3(IV)NC1]. EAG is characterized by circulating and deposited anti-α3(IV)NC1 antibodies, accompanied by focal necrotizing glomerulonephritis with crescent formation. Programmed death-1 (PD-1) receptor is preferentially expressed on activated T cells and binds two known ligands present on antigen presenting cells, PDL-1 and PDL-2. Engagement of PD-1 by its ligands results in a negative regulatory effect, with inhibition of downstream cellular signalling events and diminished cellular proliferation. In order to investigate the role of the PD-1/PDL-1 co-inhibitory pathway in development of EAG, the in vivo effects of a stimulating PDL-1/Fc fusion protein were examined after the onset of disease. Stimulation of PD-1 led to a significant reduction in albuminuria, serum urea, serum creatinine, crescent formation and tubular damage compared with controls. There was also a reduction in numbers of glomerular macrophages, CD4+ T cells, CD8+ T cells and PD1+ cells compared with controls. No reduction was observed in levels of circulating or deposited antibodies. These results demonstrate that PDL-1/Fc fusion protein is effective in treatment of glomerulonephritis and confirm the importance of the PD-1/PDL-1 T-cell co-inhibitory pathway in development of EAG. Strategies designed to stimulate this pathway may provide a novel approach to treatment of human glomerulonephritis.

Summary: Experimental autoimmune glomerulonephritis (EAG) can be induced in Wistar Kyoto (WKY) rats by immunization with the non-collagenous domain (NC1) of the alpha 3 chain of type IV collagen, α3(IV)NC1. In patients with Goodpasture's disease, the major B cell epitope is located at the N-terminus of α3(IV)NC1. In order to investigate whether B and T cell responses in EAG are directed towards immunodominant peptides within the same region of rat α3(IV)NC1, we immunized WKY rats with recombinant rat α3(IV)NC1 (positive control) and five 15-mer overlapping synthetic peptides from the N-terminus of rat α3(IV)NC1: pCol(17–31), pCol(24–38), pCol(31–45), pCol(38–52) and pCol(45–59). Positive control animals immunized with α3(IV)NC1 produced an antibody response directed towards α3(IV)NC1 and pCol(24–38). Splenic T cells from these animals proliferated in response to α3(IV)NC1 and pCol(24–38). No significant antibody or T cell responses were observed to the other peptides examined. Animals immunized with pCol(24–38) developed linear deposits of immunoglobulin G on the glomerular basement membrane, albuminuria and focal necrotizing glomerulonephritis with crescent formation by week 6 after immunization. Circulating antibodies from these animals recognized pCol(24–38) and α3(IV)NC1, and their T cells proliferated in response to pCol(24–38) and α3(IV)NC1. Animals immunized with the other peptides developed no significant immune response to α3(IV)NC1 and no disease. In conclusion, these results demonstrate that a 15-mer peptide from the N-terminus of α3(IV)NC1 [pCol(24–38)] is recognized by B and T cells from rats immunized with recombinant α3(IV)NC1, and that the same peptide is capable of inducing crescentic glomerulonephritis. Identification of this immunodominant peptide will be of value in designing new therapeutic strategies for inducing mucosal tolerance in EAG, which may be applicable to patients with glomerulonephritis.

Background. Previous studies have shown that different inbred rat strains vary in their susceptibility to experimental autoimmune glomerulonephritis (EAG). The Wistar Kyoto (WKY) rat is highly susceptible and develops crescentic glomerulonephritis, while the Lewis (LEW) rat is resistant. When immunized with collagenase-solubilized rat glomerular basement membrane (GBM), both strains produce circulating autoantibodies reactive with rat GBM by enzyme-linked immunosorbent assay, but only the WKY rat shows strong linear deposits of IgG on the GBM.

Goodpasture's, or anti‐glomerular basement membrane (GBM), disease presents with rapidly progressive glomerulonephritis and lung haemorrhage, and is caused by autoimmunity to the NC1 domain of the α3 chain of type IV collagen (α3(IV)NC1). This study examines the development of crescentic nephritis and alveolar haemorrhage in a model of Goodpasture's disease, experimental autoimmune glomerulonephritis (EAG), induced in WKY rats by immunization with rat GBM in adjuvant. An increase in circulating anti‐GBM antibodies and albuminuria was observed by week 2, which increased further by weeks 3 and 4, while a decrease in creatinine clearance was observed by week 2, which decreased further by weeks 3 and 4. The kidneys of animals with EAG showed linear deposits of IgG on the GBM and a transient glomerular infiltration by CD4+ T cells at week 2. By week 3 there were large deposits of fibrin in Bowman's space, and glomerular infiltration by CD8+ T cells and macrophages, accompanied by focal necrotizing glomerulonephritis with crescent formation. Ultrastructural studies showed glomerular endothelial cell swelling and epithelial cell foot process effacement at week 2. As the lesion progressed, capillary loops became occluded and the mesangium became expanded by mononuclear cells. By week 3 there was detachment of the endothelium from the GBM, and accumulation of fibrin beneath the disrupted endothelial cells and in Bowman's space. Occasional breaks were observed in the continuity of the basement membrane, and cytoplasmic projections from infiltrating mononuclear cells could be seen crossing the capillary wall between the lumen and the crescent. The lungs of animals with EAG showed patchy binding of IgG to the alveolar basement membrane (ABM) at week 2, and infiltration of the interstitium by CD8+ T cells and macrophages by weeks 3 and 4, accompanied by both interstitial and alveolar haemorrhage. Ultrastructural studies showed focal mononuclear cell infiltrates in alveolar walls at week 2. Occasional breaks were observed in the basement membrane and adjacent endothelium by weeks 3 and 4, together with accumulation of surfactant and erythrocytes within the alveolar spaces. This study defines for the first time the relationship between the immunological and pathological events during the evolution of EAG, and provides the basis for further work on the pathogenesis of Goodpasture's disease. Copyright © 2003 John Wiley & Sons, Ltd.