The evolution of crescentic nephritis and alveolar haemorrhage following induction of autoimmunity to glomerular basement membrane in an experimental model of Goodpasture's disease.

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 alpha3 chain of type IV collagen (alpha3(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.

Segregation of experimental autoimmune glomerulonephritis as a complex genetic trait and exclusion of Col4a3 as a candidate gene.

Experimental autoimmune glomerulonephritis (EAG), an animal model of Goodpasture's disease, can be induced in Wistar-Kyoto (WKY) rats (RT1-l) by immunization with rat glomerular basement membrane (GBM) in adjuvant. The model in this rat strain is characterized by anti-GBM antibody production accompanied by focal necrotizing glomerulonephritis with crescent formation. The main autoantigen in humans and rats has been identified as the non-collagenous domain of the alpha3 chain of type IV collagen (alpha3(IV)NC1). By contrast, Lewis (LEW) rats with the same MHC background (RT1-l), immunized with the same antigen, develop similar levels of circulating anti-GBM antibodies, but no histological evidence of nephritis. In order to investigate the genetic basis of susceptibility to EAG, we examined the response of both F1 (WKY x LEW) and backcross (BC1; WKY x F1) rats to immunization with rat GBM. F1 animals were completely resistant to the development of EAG, while BC1 animals showed a range of responses from severe crescentic glomerulonephritis to no histological evidence of disease. The results indicate that EAG is inherited as a complex trait under the control of WKY genes unlinked to the MHC. cDNA sequence analysis of alpha3(IV)NC1 in the two parental strains was identical, indicating no predicted amino acid sequence variation in the alpha3(IV)NC1 domain between these strains. Radiation hybrid mapping, using two separate PCR amplicons from rat alpha3(IV)NC1, localized rat Col4a3 to a region of chromosome 9. Since Col4a3 (encoding the autoantigen) is a candidate for susceptibility to EAG, we screened the region of rat chromosome 9 where Col4a3 is localized, using polymorphic microsatellite markers in segregating BC1 progeny. No significant linkage was detected. These results exclude Col4a3 as a recessive susceptibility gene for EAG in the BC1 progeny.