Measurement of anti-glomerular-basement-membrane antibodies by micro ELISA using insoluble antigens.

An enzyme immunoassay, using finely ground rabbit glomerular basement membrane (GBM) as an antigen, was able to detect sheep anti-rabbit GBM antibodies at serum dilutions of 1:32 000. The particulate GBM bound firmly to plastic micro ELISA plates without the aid of a linking agent, and the antigen-coated plates remained stable for several months when stored at -70 degrees C. There were no appreciable differences between amino acid compositions of ground and whole GBM, and no detectable loss of antigens occurred during the grinding procedure. Competitive inhibition assays with collagenase and pepsin digests of rabbit GBM demonstrated preservation of collagenous and non-collagenous antigens in the ground GBM. The assay should prove to be a relatively simple and highly sensitive technique for detecting antibodies to a wide spectrum of GBM antigens.