The thyrotropin (thyroid-stimulating hormone) receptor is expressed on murine dendritic cells and on a subset of CD45RB(high) lymph node T cells: Functional role for thyroid-stimulating hormone during immune activation

Thyroid-stimulating hormone (TSH), a central neuroendocrine mediator of the hypothalamus-pituitary-thyroid axis, has been shown to affect various aspe cts of immunological development and function. To gain a better understandi ng of TSH involvement within the mammalian immune system, the expression an d distribution of the TSH receptor (TSHr) has been studied by immunoprecipi tation and by flow cytometric analyses. Using highly enriched populations o f B cells, T cells, and dendritic cells, trace amounts of TSHr were precipi tated from B cells and T cells, whereas high levels of TSHr were precipitat ed from the dendritic cell fraction, Flow cytometric analyses of TSHr expre ssion on splenic and lymph node T cells revealed a major difference between those tissues in that only 2-3% of splenic T cells were TSHr(+), whereas 1 0-20% of CD4(+)8(-) and CD4(-)8(+) lymph node T cells expressed the TSHr, w hich was exclusively associated with CD45RB(high) cells and was not express ed during or after activation. The TSHr was not present on cells of the imm une system during fetal or neonatal life. However, recombinant TSH beta was found to significantly enhance the phagocytic activity of dendritic cells from adult animals and to selectively augment IL-1 beta and IL-12 cytokine responses of dendritic cells following phagocytic activation. These finding s identify a novel immune-endocrine bridge associated with professional APC s and naive T cells.