Thyrotropic hormone (TSH) regulation of triiodothyronine (T3) concentration in immune cells

Cells of the immune system (peritoneal lymphocytes, monocytes, granulocytes and mast cells as well as thymocytes) contain triiodothyronine (T-3). The aim of the present experiments was to study whether thyrotropic hormone (TSH) regulates or not the T-3 concentration of these cells. Peritoneal fluid and thymus cells of adult rats were studied by immunocytochemistry, combined with flow cytometry for triiodothyronine content with or without in-vitro TSH treatment. In addition, adult female CD1 mice were treated in vivo with 10 or 40 mU TSH and after 1 hour peritoneal immune cells were studied using the above mentioned method. Both in vitro (in rat) and in vivo (in mice) TSH treatments significantly elevated the T-3 content in each cell type. In vitro TSH 0.1 mU/ml cell suspension was enough to provoke about 50 % increase in T-3 production. T-3 concentration in immune cells seems to be regulated by TSH, similarly to the T-3 in the thyroid. Considering the large number of immune cells in an organism, TSH regulation of their T-3 content could have an important physiological and pathological role, both in and beyond the immune system.