ANALYSIS OF ANTIBODY-DEPENDENT CELL-MEDIATED CYTOTOXICITY IN AUTOIMMUNE THYROID-DISEASE

There is no consensus on the role of antibody-dependent cell-mediated cytotoxicity (ADCC) in autoimmune thyroid disease; recent reports have suggested that antibodies mediating ADCC are found particularly in pa tients with primary myxoedema, occur less frequently in Hashimoto's th yroiditis and are absent in Graves' disease. Using an ADCC assay with a single source of effector and target cells, and expressing results a s lytic units, we have found antibodies capable of mediating ADCC in 9 of 17 patients with primary myxoedema, 9 of 22 patients with Hashimot o's thyroiditis and 6 of 22 patients with Graves' disease. There was n o significant difference between the groups in this distribution. Mean levels of ADCC activity were not significantly different comparing pr imary myxoedema and Hashimoto's thyroiditis patients, although levels were lower in Graves' disease patients compared to those with Hashimot o's thyroiditis (P < 0.05). There was no correlation between TPO antib odies (total IgG or IgG subclasses) measured by ELISA and ADCC activit y. These results suggest that thyroid antigens besides TPO are involve d in ADCC and that antibodies mediating ADCC are not restricted to sub groups of patients with autoimmune thyroid disease.