INCREASE IN PERIPHERAL NATURAL KILLER CELL ACTIVITY IN PATIENTS WITH AUTOIMMUNE THYROID DISEASE

Changes in the activity and number of natural killer (NK) cells in peripheral blood in patients with autoimmune thyroid disease were examined. NK activity was measured in a 4-hr ⁵¹Cr-release assay and the number of NK cells was analyzed with FITC-conjugated monoclonal antibodies by use of an automated flow cytometer. NK activity in patients with untreated Graves' disease (n=25, 39.7+13.5%, P<0.05) and Hashimoto's thyroiditis (n=18, 41.0±14.2%, P<0.05) was high compared to the activity in non-pregnant controls (n=61, 32.6±15.0%). NK activity in patients with postpartum Graves' thyrotoxicosis (n=11, 48.6±18.9%) was markedly increased compared to the activity in non-pregnant controls (P<0.01) and in postpartum controls (n=29, 33.8±15.2%, P<0.05), although the mean ages of each group did not differ significantly. Moreover, NK activities in the thyrotoxic state were significantly higher than those in the euthyroid state in the same patients with postpartum Graves' thyrotoxicosis or with postpartum destructive thyrotoxicosis. The number of CD16 positive cells increased in patients with postpartum Graves' thyrotoxicosis. However the number of CD 16 and CD57 positive cells were normal in all other groups of patients. These results indicate that an increase of NK activity is associated with exacerbation of autoimmune thyroid disease both in Hashimoto's thyroiditis and in Graves' disease and suggest that NK cells might have an important role for the control of disease activity in autoimmune thyroid disease.