HUMAN GOODPASTURE ANTI-ALPHA-3(IV)NC1 AUTOANTIBODIES SHARE STRUCTURALDETERMINANTS

To examine the structural relationship among autoantibodies produced b y individuals with anti-GEM antibody-mediated disease, a polyclonal an ti-idiotype directed against human anti-alpha 3(IV)NC1 antibodies was produced and then used to study autoantibodies from other patients. Fo r this purpose, anti-alpha 3(IV)NC1 antibodies (anti-GEM), derived fro m a single patient (LL) with high titer and typical anti-GEM antibody specificity, were isolated using recombinant alpha 3(IV)NC1-sepharose affinity chromatography. Following hyperimmunization of rabbits with a nti-GEM IgG, irrelevant rabbit anti-human IgG antibodies were removed from the antiserum using a human IgG-sepharose column. The rabbit anti -alpha 3(IV)NC1 antibodies (anti-Id GEM) effluent bound to human anti- GEM antibodies, but it did not bind to either normal human IgG or reco mbinant alpha 3(IV)NC1 protein. The Id-anti-Id interaction was conform ationally dependent on intact heavy and light chains of the anti-alpha 3(IV)NC1 antibodies (ELISA and Western blotting). A competitive immun oassay was developed to evaluate structural and potential genetic rela tionships among anti-alpha 3(IV)NC1 antibodies from different patients . All patients tested (9 of 9) had a substantial fraction (producing > 50% inhibition) of anti-GEM antibodies expressing Id-GEM. The results indicate that shared determinants are expressed by anti-GEM antibodie s from different individuals, and they raise the possibility that comm on genetic elements are used to encode them. These regions are potenti al targets for design of reagents to regulate autoreactive B cells and /or interfere with pathogenic antibody-GEM interactions, in individual s with anti-GEM antibody mediated diseases.