The Presence of Anti-Glomerular Basement Membrane Antibodies in Peripheral Blood

Abstract

The use of immunofluorescent assay for circulating anti-glomerular basement membrane (anti GBM) antibodies is described. Groups of people studied for the presence of anti-GBM antibody included: a) normals; b) immune-complex glomerulonephritic patients; c) anti-GBM antibody-mediated nephritic patients; d) a hemodialysis-maintained group of kidney disease patients; and e) an allergy clinic group. Anti-GBM antibodies were found in the circulation only in patients with anti-GBM antibody-mediated nephritis. Paired-label isotopic studies to determine the percentage fixation of kidney-fixing antibodies, combined with serial dilution of the same anti-GBM antibody-containing sera, allowed estimation of the sensitivity of the assay to be in the range of 0.1 to 1.0 µg/ml antibody content. Despite the sensitivity of the technique and its specificity, two principal handicaps were encountered: a) only 40% of people known to have anti-GBM antibody-mediated glomerulonephritis were shown to have circulating anti-GBM antibodies, and b) several sera were encountered which fixed with wide anatomical definition to the target substrate and made it difficult to recognize the presence of anti-GBM antibodies in such sera.