Fc receptor-bearing blood mononuclear cells in thyroid disorders: increased levels in patients with subacute thyroiditis.

Blood mononuclear cells bearing Fc receptors for immunoglobulin G were measured in patients with thyroid disorders as the percentage of EA rosette-forming cells (% EA-RFC). Levels were normal in patients with untreated Graves' hyperthyroidism, Graves' ophthalmopathy, and Hashimoto's thyroiditis. On the other hand, the % EA-RFC was increased in eight of nine patients with subacute thyroiditis (SAT) tested during the acute phase, returning to normal during recovery. Levels were normal in all five patients with "silent" thyroiditis tested. The majority of the Fc receptor-bearing cells in SAT patients was shown to be phagocytic. There was no evidence for increased killer cell or suppressor cell activity, functions which reside in Fc receptor-bearing mononuclear cell populations, in SAT patients. There was no close correlation between the % EA-RFC and parameters of thyroid damage (erythrocyte sedimentation rate and serum T4 levels) or thyroid antibody titers. While an increase in the % EA-RFC in SAT patients may represent a nonspecific response to a viral inflammation of the thyroid gland, the abnormalities may be markers of a more specific immunological response to thyroid antigen release. Abnormalities of blood mononuclear cell numbers in Graves' hyperthyroidism and SAT are reviewed.