To investigate the immunological process in various thyroid disease, we measured interferon-alpha, -gamma (IFN-α,-γ), natural killer (NK) activity, and lymphocyte subsets in the peripheral blood of 27 patients with Basedow's disease (BD) (M: F=9: 18), 8 with Hashimoto's thyroiditis (HT) (2: 6), 5 with idiopathic hypothyroidism (IHT) (1: 4), and normal controls (C).
IFN-α, -γ levels were measured by bioassay with Dye-uptake method, and NK activity was measured by the LDH method. The mean_??_SD levels of IFN-γ in BD, HT, IHT, and C (N=217) were 173.9±88.0, 288.0±134.9, 120.4±38.0 and 173.9±88.0IU/ml, respectively. The IFN-γ level was higher in HT (p<0.05) than in controls, and lower in BD (p<0.02). Moreover, this IFN-γ level did not correspond with the titers of thyroid hormones; TSH, anti-microsome antibody, and anti-TSH-receptor antibody in peripheral blood. However, IFN-α levels and NK activity in the patients of every group were similar to those in controls. The ratios of lymphocyte subsets of peripheral blood were measured by cytofluorometry with monoclonal antibodies. The mean±SD levels of T cells in BD, HT, IHT and C were 75.9±7.0, 83.4±7.2, 85.2±5.7, 82.3±5.8%, and those of B cells were 17.5±6.1, 10.9±4.2, 8.0±5.8, 10.9±5.0%, respectively. The ratio of T cells was higher in IHT (p<0.05) and lower in BD (p<0.01) than in controls. However, the ratio of B cells was lower in IHT (p<0.05), and higher in BD (p<0.01).
Now it has been reported that the local IFN-γ plays an important role in the onset, maintenance and development of BD. In this study, the peripheral IFN-γ level in BD was low despite high levels in the thyroid gland. We speculate these paradoxical IFN-γ levels are related to auto-regulation of cytokines, or T lymphocyte impairment in autoimmune thyroid diseases.
