Peripheral K cells in Graves' disease and Hashimoto's thyroiditis in relation to circulating immune complexes

A plaque assay was employed to quantify the number of peripheral K cells in autoimmune thyroid diseases. The percentages of peripheral K cells determined were 3.1 +/- 2.2% and 3.3 +/- 1.3% (mean +/- SD) in forty-one patients with Graves' disease and twenty-two patients with Hashimoto's thyroiditis, respectively, which were significantly lower than 5.3 +/- 2.5% in 22 normal subjects. Circulating immune complexes (ICs) were measured by three different methods. The positivity of these ICs was investigated in relation to the level of peripheral K cells. The percentage of peripheral K cells in the patients positive for ICs was found to be lower than that in the patients negative for any ICs. Moreover, it was observed that the number of detectable K cells from a normal subject was significantly decreased by incubating the K cells with sera of patients positive for ICs. These results suggest that the decrease of peripheral K cells in the patients with autoimmune thyroid diseases may be due to saturation of K cell Fc receptors by binding ICs.