Expression of muscarinic cholinergic receptors on lymphocytes during rheumatoid arthritis.

The level of muscarinic receptors on lymphocytes from rheumatoid arthritis (RA) patients in comparison with healthy individuals was determined by the binding studies of a specific muscarinic ligand [3H]-QNB in the presence of the competitive antagonist atropine. The response to phytohaemagglutinin and the influence of acetylcholine on this process in patients' lymphocytes was also studied. We have found direct correlation among PHA stimulation indices, the level of muscarinic receptors, and the influence of acetylcholine on PHA stimulation indices. Differences in these parameters occurring in systemic forms of RA as compared to other RA patients are also described and their possible mechanism discussed. The influence of cholinergic stimulation on the reactivity of lymphocytes after PHA in different forms of RA could depend on the number of muscarinic receptors present on the lymphocyte surface, as well as on the activity of soluble factors, which could modulate the functional state of the receptors.