Effect of hypo- and hyperthyroidism on the balance between helper and suppressor T cells in rats
Abstract. The proportion of total, helper and suppressor T lymphocytes among mononuclear cell preparations from blood and spleen of rats made hypo- and hyperthyroid was measured using three monoclonal antibodies specifically directed against total, helper and suppressor T cells. Compared to normal rats, hypothyroid (thyroidectomized or treated with 6-propyl-2-thiouracil (PTU)) rats had a decreased proportion of suppressor T cells in the spleen, which produced an increase in the helper/suppressor T cells ratio. The opposite alterations (increased suppressor T cells and decreased ratio) was found in the blood of the same animals. Triiodothyronine (T3) added to PTU in the drinking water prevented these alterations. Animals treated with high doses of T3 for 17 days did not develop any alteration either in the proportions or in the ratio of helper/suppressor T cells. Our results suggest that hypothyroidism but not hyperthyroidism alters the normal balance between helper and suppressor T cells in rats.