Studies on autoimmune mechanisms of thyroglobulin autoantibody in autoimmune thyroid disease.
In order to clarify the autoimmune mechanisms of anti-Tg antibody (anti-TgAb) in autoimmune thyroid disease (AITD), a series of examinations were conducted in patients with Graves' disease (n = 59), Hashimoto's thyroiditis (n = 63) and healthy controls (n = 38). Our findings can be summarized as follows: 1) The distribution of anti-TgAb was measured by IgG subclass ELISA. IgG1 and/or IgG4 antibodies formed the major anti-Tg response, but in some patients, IgG2 anti-Tg tend to be the predominant response. We used ELISA to determine an IgG1 anti-Tg bound to Tg that had already interacted with IgG2 Tg-antibody (and vice versa). The results substantiated the view that TgAb of a different IgG subclass interact with different epitopes on Tg. 2) Human antiidiotypic (anti-Id) antibodies to anti-Tg antibody occur spontaneously in the AITD. These anti-Id antibodies can be divided into two categories based on properties of their binding sites. One type acts like a 'internal image' of Tg antigen which shown Ab2 beta activity. Another type has Ab2 alpha activity that recognizes Id determinants in the framework region common among anti-Tg antibody. 3) We also examined the competitive binding assay between TgAb and TgAb F(ab')2 fragments, and demonstrated differences in the TgAb repertoires between patients. 4) Soluble IL-2 receptor (IL-2R) of patients significantly increased as compared with normal subjects and IL-2R values in GD were higher than those in HT (p < 0.001). Therefore, IL-2R is regarded as a useful marker for disease activity.
Department of Clinical Laboratory Medicine, Hiroshima University School of Medicine, Japan.
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D000328:Adult; D000368:Aged; D000906:Antibodies / Q000097:blood*; D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D005260:Female; D006111:Graves Disease / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D008297:Male; D008875:Middle Aged; D015375:Receptors, Interleukin-2 / Q000032:analysis; D013954:Thyroglobulin / Q000276:immunology*; D013967:Thyroiditis, Autoimmune / Q000276:immunology*
D000906:Antibodies; D000888:Antibodies, Anti-Idiotypic; D007074:Immunoglobulin G; D015375:Receptors, Interleukin-2; D013954:Thyroglobulin