Glomerular basement membrane autoantibodies

Anti-glomerular basement membrane (anti-GBM) disease is a prototype of autoimmune disease. The disease can be transferred with the antibodies and there is a strong correlation with certain human leukocyte antigen (HLA) genes. The pathogenic epitope on the NC1 domain of the 3-chain of type IV collagen is well characterized and only antibodies against this epitope correlate with disease. The diagnosis is made on the combination of rapidly progressive renal failure and the demonstration of anti-GBM antibodies. The course is sometimes complicated by severe lung haemorrhage, and untreated anti-GBM disease has a poor prognosis. Early diagnosis and treatment with immunosuppression and plasma exchange leads to improved prognosis. Because of its clinical significance and high predictive value, anti-GBM antibody analysis is indicated in most cases of unknown renal failure with microhaematuria, especially if progression is rapid. Circulating anti-GBM antibodies can be detected with indirect immunofluorescence (IF) or enzyme-linked immunosorbent assay (ELISA). In indirect IF, serum from the patient is overlaid with a section of normal kidney. A good substrate and a good pathologist are needed because unspecific staining can be difficult to distinguish from the true linear staining pattern. Low levels of circulating autoantibodies cannot usually be detected with indirect IF. There are several ELISA kits available on the market. The performances of these assays depend on the purity of the antigen preparation, but are generally good.