Antibody-dependent Cell-mediated Cytotoxicity as a Prognostic Indicator in the Medical Treatment of Graves´ Disease

Abstract

Background: The several forms of treatment of Graves´ disease-thyroidectomy, antithyroid drugs and radioiodide therapy-are in wide use now. But which therapy is best is a matter of debate. Some authors reported that in patients who underwent thyroidectomy, higher titers of serum antimicrosomal antibody were associated with 1) higher formation rates of germinal centers, 2) more lymphocyte infiltration in the thyroid tissue, 3) higher incidence of hypothyroidism, and 4) lower incidence of recurrence. We were interested in the relationship of thyroid autoantibody titers, ADCC(antibody-dependent cell-mediated cytotoxicity) activity and the clinical response to antithyroid medication. Methods: We measured ADCC activities from patients in Graves´ disease(n-48), Hashimoto´ thyroiditis(n-17) and normal control(n-9). The patients of Graves´ disease were followed up for more than 1 year, and they were grouped into A(n-17, well responsed group to antithyroid medication) and B(n-31, poorly responsed group). We examined ADCC activities of patients´ sera by chromium release assay. Results: 1) Mean age of patients with Graves´ discase was 34.42±10.4 years and 15 patients were male(31 %). 2) Results of thyroid function tests of the Graves´ patients were T₃ 585.9±255.3 ng/dL, T₄ 21.3 ± 12.2 ㎍/dL, TSH 0.11 ± 0.06 μIU/mL. Concentrations of antimicrosomal antibody, antithyroglobulin antibody and thyrotropin binding inhibitory immunoglobulin were 1279.1 ±1486.7 IU/mL, 488.1 ±751.1 IU/mL, and 38.5 ±33.4 U/L respectively. 3) There was no significant difference between levels of thyroid hormones or concentrations of thyroid autoantibodies and ADCC activities in graves´ patients. 4) The ADCC activity of the Graves´ patient group(24.49%) was significantly higher than that of the normal control group(3.76%), and significantly lower than that of the Hashimoto´s thyroiditis group(36.34%). 5) There was no significant difference in ADCC activity between group A(18.24±13.44%) and B(27.91±20.02%). Conclusion: From this results, we suggested that ADCC activity seems to be no value as a prognostic factor in predicting the response to antithyroid drugs in Graves´ disease patients. But, further studies, larger number of patients and long-term follow up, are needed.