Effect of human thyroglobulin on the production of platelet activating factor from peripheral blood mononuclear cells from patients with autoimmune thyroid diseases

Platelet activating factor (PAF), a phospholipid mediator, has been found to play a role in immune reactions, as well as in many pathophysiological alterations in certain disorders. To determine whether there might be a potential role of PAF in the development of autoimmune thyroid diseases (AITD) we have measured in vitro production of PAF by cultures of pokeweed mitogen-stimulated peripheral blood mononuclear cells (PBMC) obtained from 13 patients with Hashimoto's thyroiditis (HT) and 22 patients with Graves' disease (GD), as well as 18 normal control subjects. Similarly, the levels of PAF in cultures of PBMC after relevant [human thyroglobulin (Tg) and human thyroperoxidase (TPO)] antigenic stimulation in the same preparations were measured by a RIA kit. The basal values of PAF were significantly higher in the PBMC preparations from HT patients than in other two groups. In HT preparations, but not in controls, Tg antigen significantly increased the production of PAF. In GD preparations the response to Tg antigen was also present, but the release of PAF did not reach the levels in control group of preparations. Significantly lower values of PAF production were found in preparations from hyperthyroid GD when compared to the results of preparations from GD patients who were euthyroid and to the results of normal control preparations. The type of treatment and chronicity of disease may also have played some role in these findings, since those treated with radioactive iodine had lower values than those patients who became euthyroid using only antithyroid drugs. It is not evident from these preliminary studies what the nature of PAF participation may be in the immune events leading to the development of AITD, but these observations at least imply some interaction in these events.