Thyroid cells in Graves' disease and Hashimoto's thyroiditis stimulate allogeneic T cells when pretreated with phorbol ester

Publisher Website
Google Scholar
Abstract
OBJECTIVE To assess the capacity of thyroid follicular cells to function as antigen presenting cells, we have examined their ability to stimulate allogeneic T cells.DESIGN Thyroid follicular cells were pretreated with interferon‐γ or phorbol myristate acetate, washed thoroughly, and their capacity to induce allogeneic T cell proliferation was determined.PATIENTS Thyroid cells were prepared using thyroidectomy specimens from eight patients with Graves' disease, one with Hashimoto's thyroiditis and two with non‐toxic multinodular goitre.MEASUREMENTS T cell 3H‐thymidine incorporation was measured after a 16‐hour incubation period with the isotope, 3 days after co‐culture of T cells and thyroid cells.RESULTS Four of the eight thyroid cell preparations from thyroid autoimmunity patients failed to stimulate T cells, although there was a significant, weak stimulation for the whole group (P <0.05): interferon‐γ pretreatment had no effect on this. Phorbol myristate acetate pretreatment significantly increased the ability of thyroid cells (from both autoimmune and multinodular glands) to stimulate T cells (P <0.05); this was time and concentration dependent. Cell fixation after PMA treatment did not abolish this stimulatory activity, which could be transferred by supernatants from unfixed cells; exogenous interleukin‐1 did not mimic the activity.CONCLUSIONS Thyroid cells expressing major histocompatibility complex class II molecules only weakly and inconsistently stimulate allogeneic T cells, compared to thyroid cells pretreated with phorbol myristate acetate, a difference which may be due to the expression of an unidentified co‐stimulatory signal induced by phorbol ester.