T, B and K cells in autoimmune thyroid disease

The K-cell cytotoxic activity of peripheral blood lymphoid cells from 104 patients with autoimmune thyroid disease and from age and sex matched control subjects was measured using chicken erythrocytes as target cells. Patients with Hashimoto thyroiditis,primary hypothyroidism and thyrotoxicosis who were either newly diagnosed and untreated or had received therapy for less than or equal to 1 year showed a significant increase in K-cell cytotoxic activity. Patients who had received treatment for greater than 1 year and less than or equal to 5 years showed no such comparable increase in cytotoxic activity. Within the group of patients with untreated thyrotoxicosis it was found that K-cell cytotoxic activity was related to both goitre size and serum antibody titre. Thus patients with little or no goitre showed a highly significant elevation of cytotoxic activity whereas patients with moderate to large goitres gave values within the normal range. Similarly patients with no detectable serum thyroid autoantibodies showed high K-cell activity while patients with positive antibody titres did not. It was also shown that neither the absolute number nor the proportion of circulating T and B lymphocytes in patients with autoimmune thyroid disease as assessed by the sheep red cell rosette method and by indirect immunofluorescence was significantly different from that observed in the normal control population. No correlation was found between peripheral blood K-cell cytotoxic activity and the percentage of circulating null cells, i.e. 100-(percentage T + percentage B) in either patients or control subjects.