The Inhibitory Effect of the Muscarinic Agonist Pilocarpine on Lymphocyte Activation Involves the IL-2 Pathway and the Increase in Suppressor Cell Function

Abstract

The inhibition of lymphocyte DNA synthesis by the cholinergic muscarinic agonist pilocarpine (5 × 10^-4 M) was not reversed by addition of exogenous recombinant Interleukin-2 (100–1000 IU/ml). Pilocarpine did not inhibit Interleukin-2 (IL-2) production by human peripheral blood mononuclear cells but decreased the number of interleukin-2 receptor bearing cells (TAC positive cells). Furthermore, pilocarpine increased the CD8:CD4 T lymphocyte ratio enhancing the suppressor cell function. All these effects were blocked by the muscarinic antagonist atropine (1 × 10^-6 M). As described for the specific lymphocyte nicotinic stimulation, the pure cholinergic muscarinic stimulation inhibits lymphocyte proliferation by enhancing suppressor activity.

Key Words:

• neuroimmunomodulation
• muscarinic receptors
• suppressor activity
• IL-2
• pilocarpine
• lymphocyte activation