DOPAMINE-RECEPTORS ON HUMAN T-LYMPHOCYTES AND B-LYMPHOCYTES

The presence of functional dopamine receptors on differentiated cells of the mammalian immune system is still under discussion. This study h as utilized (-)-[H-3]sulpiride as a ligand, to detect the presence of recognition sites of the dopamine D2 receptor family on human T- and B -lymphocytes. The (-)-[H-3]sulpiride binding was of high affinity (K(d ) 0.9 nM +/- 0.2 nM), specific, saturable (B(max) 10.2 +/- 1.4 fmol/10 (6) cells) and reversible. The pharmacological characterization of the recognition site suggests similarities mainly with the D2 and D4 rath er than D3 subtype of dopamine receptor. Furthermore, dopamine treatme nt was able to reduce the intracellular cAMP levels of lymphocytes sti mulated with forskolin, thus suggesting a potential functional signifi cance of this dopamine receptor in mediating neural-immune interaction s.