Objective: 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.
Methods: 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.
Results: 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.
Conclusion: 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.