In vitro studies on the control of thyroid autoantibody synthesis

A current hypothesis suggests that autoimmune responses are prevented in normal individuals by a population of suppressor cells. We have investigated this using a system in which thyroid autoantibodies are synthesised in culture by peripheral blood mononuclear cells (PBM) from patients with Hashimoto's thyroiditis. A group of 8 Hashimoto patients and 17 normal subjects were used in the study. PBM from the group of patients did not differ significantly from those of the control group in terms of their ability to synthesise IgG in culture, to respond to allogeneic cells or to PHA. (Nor were any genetic differences observed between the two groups in terms of HLA-A, B or C antigens.) In 6 co-culture experiments involving equal numbers of PBM from patients and normal donors, inhibition of thyroid antibody production was not observed. Additionally, T-cell enriched populations from 2 normal donors were unable to specifically inhibit thyroid antibody synthesis by Hashimoto B-cell enriched fractions from 2 Hashimoto patients. Consequently, we were unable to show suppressor cell activity in normal PBM and it is suggested that these cells may need to be activated by antigen before their presence can be demonstrated.