Muscarinic cholinergic binding sites on intact human lymphocytes

Using the muscarinic chalinergic ligand ³H]-quinuclidinyl benzilate, we have demonstrated that intact, viable human lymphocytes possess specific muscarinic binding sites. The binding is saturable, proportional to cell number, and is displaceable by atropine, benztropine, trihexyphenidyl and scopolamine. The apparent kd is 67 nM and the number of binding sites per cell is on the order of 5 × 10⁴. Not only do these findings provide a pharmacological basis for the observed effects of muscarinic agents on lymphocyte function, they also demonstrate the utility of human peripheral blood lymphocytes for investigation of abnormalities of the muscarinic cholinergic system.