Lymphocyte transformation in response to human thyroid extract in patients with subacute thyroiditis

Seven patients with subacute thyroiditis were studied for evidence of cell-mediated immunity (CMI) to human thyroid extract, as judged from lymphocyte transformation responses, measured by the increase in labeled thymidine uptake in vitro. Significant transformation was observed in lymphocytes from five of the seven patients with active subacute thyroiditis, and in the lymphocytes from only three of 15 patients with Graves disease (x2, P EQUALS 0.036). Repeated studies of lymphocyte transformation were done in four of the patients with subacute thyroiditis, three of whom initially showed abnormal responses. By eight weeks after initial studies, when all patients were in clinical remission without treatment, transformation responses were within the normal range. Thyroid antibodies were absent or present in low titer (is less than 1:100) in sera of patients with subacute thyroiditis, and became undetectable by eight weeks in those patients initially positive. In contrast, significant titers of antithyroid antibodies were frequently present in patients with Graves' disease. The present studies have shown the occurence of CMI to thyroid antigens during the active phase of subacute thyroiditis. The abnormality was transient, however, since it disappeared when the disease had resolved. These findings strongly suggest that the release of thyroid antigen leading tothe development of a cell-mediated immune responses is not in itself sufficient to initiate chronic immunological disease of the thyroid. If, as some have suggested, Hashimoto's disease or Graves' disease are characterized by a permanent disorder of CMI, then in these diseases either the antigenic stimulus is persistent or there exists an intrinsic disorder of immune surveillance.