TRH RECEPTOR ON IMMUNE CELLS - IN-VITRO AND IN-VIVO STIMULATION OF HUMAN LYMPHOCYTE AND RAT SPLENOCYTE DNA-SYNTHESIS BY TRH

This work examined whether (1) immune cells express thyrotrophin relea sing hormone (TRH) receptor mRNA and (2) TRH modulates lymphocyte acti vation. By Northern blot of RNA extracted from human peripheral blood mononuclear cells (PBMC) and rat splenocytes, a single TRH receptor mR NA band of about 3.8 kb (identical to that obtained from pituitary cel ls) was obtained, under both basal and stimulated conditions. A signif icant increase in DNA synthesis was observed in phytohemagglutinin-sti mulated PBMC and concanavalin A (Con A) stimulated splenocytes when TR H (10(-6) M-10(-12) M) was added. After 5, 30, 60, 180 min and 24 h of TRH administration in vivo, a significant increase in the rat splenoc yte proliferative response to Con A was observed. In vivo administrati on of anti-rat TSH antibody (1/1000) blocked the increase observed aft er 30 min of TRH administration on the Con A stimulated splenocyte res ponse. TRH possess immunostimulatory functions directly via its recept or and indirectly via release of other immunostimulatory factors such as thyrotrophin.