Background: Goodpasture (GP) syndrome is defined by the clinical association of pulmonary haemorrhage with rapidly progressive glomerulonephritis. The disease is caused by pathogenic autoantibodies directed against type IV collagen, which is a major structural component of glomerular basement membranes (GBM).
Methods: The non-collagenous domains (NC1) of all six human type IV collagen alpha chains was produced in E. coli as recombinant fusion proteins with glutathione-S transferase. Sera from 10 patients with different types of anti-GBM nephritis, including GP syndrome, were tested for reactivity with the six proteins using immunoblotting of denatured and reduced proteins and ELISA without reduction.
Results: All 10 sera reacted with the alpha 3 (IV) collagen chain by immunoblotting and ELISA. One serum also recognized the alpha 2(IV), alpha 4(IV), alpha 5(IV) and alpha 6(IV) chains by immunoblotting. ELISA measurements revealed reactivity of several other sera with alpha 2(IV), alpha 4(IV) or alpha 6(IV) but not with alpha 5(IV) collagen chains. No reactivity was observed with the alpha 1(IV) chain.
Conclusion: Autoantibodies in anti-GBM nephritis may not be directed only against the alpha 3(IV) collagen chain and they frequently recognize conformational epitopes.