Interaction of thyroid-stimulating antibody with Graves' thyroid-stimulating hormone-binding antibody

OBJECTIVE: Evidence of anti-thyroid-stimulating hormone (TSH) antibody in Graves' serum has been reported. We found that extremely high Graves' anti-TSH antibodies neutralized other Graves' thyroid-stimulating antibody (TSAb) activity. METHOD: TSAb-IgG was affinity-purified by Sepharose-bound Graves' anti-TSH antibody (extremely high). RESULT: The thyroid-stimulating activity in affinity-purified TSAb-IgG increased about 4-5 times compared to that before purification. TSH-binding inhibitory immunoglobulin (TBII) activity in affinity-purified TSAb-IgG also increased using TSH receptor-coated tube assay. A similar increase of thyroid-stimulating activity accompanied with TBII activity was also observed in affinity-purified TSAb-IgG-F(ab')(2). CONCLUSION: This suggests the possibility that either TSAb may be an anti-idiotypic antibody against anti-TSH antibody or anti-TSH antibody may be an anti-idiotypic antibody against anti-TSH receptor antibody.