Evidence for circulating immune complexes in thyroid disease.

Anti-complementary activity was detected in the sera of 23 (59%) out of 39 patients with Hashimoto thyroiditis; in 10 (29%) out of 34 patients with primary hypothyroidism; in six (17%) out of 36 patients with thyrotoxicosis; and in only six (8%) out of 78 control subjects. Fractionation of Hashimoto sera by Sephadex G-200 chromatography showed that the anti-complementary activity was founding fractions of larger molecular size than monomeric IgG, being localized predominantly in the ascending limb of the second elution peak, suggesting that it was in the form of small immune complexes.