Analysis of the clonal origins of autoantibodies against thyroglobulin and DNA in autoimmune thyroiditis and systemic lupus erythematosus.

We have analysed the isoelectric focusing (IEF) spectra of antithyroglobulin autoantibodies in the sera of patients with autoimmune thyroiditis, and of anti-dsDNA autoantibodies in the sera of patients with systemic lupus erythematosus (SLE), NZB/NZW F1 hybrid, MRL-lpr/lpr and MRL/++ male and female mice. Ninety-two per cent of patients with anti-thyroglobulin autoantibodies had a polyclonal spectrotype compared with only 25% of SLE patients analysed for anti-dsDNA. Fifty-five per cent of the latter had monoclonal spectrotypes, the remainder being either biclonal or having a dominant clone on a polyclonal background. By contrast, only two out of 61 autoimmune thyroiditis patients expressed monoclonal anti-thyroglobulin autoantibodies. All of the lupus mice had highly restricted spectrotypes (monoclonal or biclonal) of anti-dsDNA autoantibodies. The implications of these results for the aetiology of autoimmunity are discussed.