Macrophages with genetic disruption of α7, β2, or β4 subunit of nicotinic acetylcholine receptor (nAChR) attenuate the immunosuppressive effect of nicotine. Bone marrow–derived macrophages (BMM) of wild-type (WT) C57BL/6 and (A) α7-nAChR knockout (KO) mice, (B) β2-nAChR KO mice, and (C) β4-nAChR KO mice were incubated with 10% CSE for 1 hour before infection with MTB H37Rv. At 1 hour (Day 0) and 2 and 4 days after infection, intracellular MTB was quantified. Data shown are the mean (±SEM) of three independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001 compared with WT BMM + CSE. (D) [125I]epibatidine binding to detect β2 and β4 subunits of the nAChR on WT BMM. R, resistant; S, sensitive. Data shown are the mean (±SEM) of four independent experiments. *P < 0.05.