IgG SUBCLASS DISTRIBUTION OF THYROID AUTOANTIBODIES: A ‘FINGERPRINT’ OF AN INDIVIDUAL'S RESPONSE TO THYROGLOBULIN AND THYROID MICROSOMAL ANTIGEN

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Abstract
SUMMARY: The IgG subclass distribution of autoantibodies to thyroglobulin and thyroid microsomal antigen was studied in 21 patients with Graves' disease during fluctuations in total IgG class autoantibody levels induced by various forms of therapy. In addition, changes in autoantibody subclass distributions were investigated during the natural course of Hashimoto's disease in seven patients taking thyroxine. The autoantibodies were principally of subclasses IgGl and/or IgG4 in Graves' patients although IgG2 contributed significantly to thyroglobulin antibodies in 5/7 Hashimoto sera. In Graves' disease the distribution of microsomal and thyroglobulin antibodies among the IgG subclasses remained essentially unchanged over periods of 6 months‐2 years whether autoantibody levels decreased during carbimazole therapy or increased transiently following 13lIodine treatment or subtotal thyroidectomy. Similar observations were made for thyroglobulin antibodies in Hashimoto patients studied over 2½‐4 years; furthermore, the IgG subclass distribution of microsomal antibodies was usually different from that of thyroglobulin antibodies in the same patient. These observations suggest that the microsomal and/or thyroglobulin antibody subclass distribution is characteristic for a particular individual and may be regarded as the ‘fingerprint’ of an individual's response to these thyroid autoantigens.