Mol088484 50..61

Smoking is a common addiction and a leading cause of disease. Chronic nicotine exposure is known to activate nicotinic acetylcholine receptors (nAChRs) in immune cells. We demonstrate a novel role for a4 nAChRs in the effect of nicotine on T-cell proliferation and immunity. Using cell-based sorting and proteomic analysis we define an a4 nAChR expressing helper T-cell population (a4CD3CD4) and show that this group of cells is responsive to sustained nicotine exposure. In the circulation, spleen, bone marrow, and thymus, we find that nicotine promotes an increase in CD3CD4 cells via its activation of the a4 nAChR and regulation of G protein subunit o, G protein regulated–inducer of neurite outgrowth, and CDC42 signaling within T cells. In particular, nicotine is found to promote a helper T cell 2 adaptive immunologic response within T cells that is absent in a4 /2 mice. We thus present a new mechanism of a4 nAChR signaling and immune regulation in T cells, possibly accounting for the effect of smoking on the immune system.