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Thyroid cells in Graves' disease and Hashimoto's thyroiditis stimulate allogeneic T cells when pretreated with
1Department of Medicine, University of Sheffield, UK.
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-gamma 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-gamma 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.