No abstract

Nicotine has been shown to affect B lymphocyte immune response. In this study, we have explored the presence of nicotinic receptors in B lymphocyte-derived cell lines, myeloma X63-Ag8 and hybridoma 1D6. We found that myeloma expressed on average 10,170 Ϯ 1,100 [ 3 H]epibatidine and 6,730 Ϯ 370 125 I-␣-bungarotoxin binding sites per cell, thus reflecting the presence of both homomeric and heteromeric nicotinic receptors. More specifically, the presence of ␣4-and ␣7-containing nicotinic receptor subunits was demonstrated in both myeloma and hybridoma cells with subunit-specific antibodies. It was significantly higher in dividing than in resting cells. Long-term exposure to nicotine, at physiological concentration found in smokers, resulted in up-regulation of both ␣4 and ␣7 subunits in hybridoma cells. Additionally, nicotine stimulated hybridoma cell proliferation, whereas it decreased antibody production. In contrast, ␣7-specific snake toxins inhibited cell proliferation but increased antibody production. It is concluded that myeloma and hybridoma cells express ␣4-and ␣7-containing nicotinic receptors, which participate in regulating cell proliferation and function.