Differential involvement of \u3b14\u3b22, \u3b17 and \u3b19\u3b110 nicotinic acetylcholine receptors in B lymphocyte activation in vitro

Mouse B lymphocytes express several nicotinic acetylcholine receptor (nAChR) subtypes, their exact functions being not clearly understood. Here we show that \u3b17 nAChR was present in about 60%, while \u3b14\u3b22 and \u3b19(\u3b110) nAChRs in about 10% and 20% of mouse spleen B lymphocytes, respectively; Balb/c and C57Bl/6 mice possessed different relative amounts of these nAChR subtypes. \u3b14\u3b22 and \u3b17, but not \u3b19(\u3b110) nAChRs, were up-regulated upon B lymphocyte activation in vitro. Flow cytometry and sandwich ELISA studies demonstrated that \u3b17 and \u3b19(\u3b110) nAChRs are coupled to CD40, whereas \u3b14\u3b22 nAChR is coupled to IgM. B lymphocytes of both \u3b17(-/-) and \u3b22(-/-) mice responded to anti-CD40 stronger than those of the wild-type mice, whereas the cells of \u3b22(-/-) mice responded to anti-IgM worse than those of the wild-type or \u3b17(-/-) mice. Inhibition of \u3b17 and \u3b19(\u3b110) nAChRs with methyllicaconitine resulted in considerable augmentation of CD40-mediated B lymphocyte proliferation in cells of all genotypes; stimulation of \u3b14\u3b22 nAChRs with epibatidine increased the IgM-mediated proliferation of the wild-type and \u3b17(-/-), but not \u3b22(-/-) cells. Inhibition of \u3b19(\u3b110) nAChRs with \u3b1-conotoxin PeAI exerted weak stimulating effect on CD40-mediated proliferation. This nAChR subtype was up-regulated in \u3b17(-/-) B-cells. \u3b17 nAChRs were found recruited to immune synapses between human T and B lymphocytes, both of which produced acetylcholine. It is concluded that \u3b17 nAChR fulfills inhibitory CD40-related mitogenic function, \u3b14\u3b22 nAChR produces a stimulatory IgM-related effect, while \u3b19\u3b110 nAChR is a "reserve" receptor, which partly compensates the absence of \u3b17 nAChR in \u3b17(-/-) cells. Acetylcholine is an additional mediator to modulate activation of interacting T and B lymphocytes