Qualitative aspects of thyroglobulin antibodies in Hashimoto's thyroiditis and Graves' disease

We have tried to characterize the thyroglobulin antibodies (TgAb) involved in Hashimoto's thyroiditis and Graves' disease by studying their affinity constants and binding capacities. Two populations of antibodies were found in half of the patients with either disease, TgAb(1) with a high affinity (K(1)) but a low binding capacity (B(1)) and TgAb(2) with a lower affinity (K(2)) but a much higher binding capacity (B(2)). The mean affinity constants and binding capacities were similar in the two diseases. In the other half of the patients only one population of antibody was present, with a low affinity constant (K(t)) and a very high binding capacity (B(t)), thus comparable to TgAb(2). The mean K(t) and B(t) were similar in the two diseases. From these results it would appear that circulating thyroglobulin antibodies in Hashimoto's thyroiditis and Graves' disease are similar in their affinity constants and binding capacities, so that these characteristics do not reflect the different pathogenesis of each condition.