title: Cigarette smoke impairs cytokine responses and BCG containment in alveolar macrophages.
abstract: BACKGROUND
  There is a strong epidemiological link between smoking and tuberculosis (TB), but the association is confounded by socioeconomic and other factors. A direct relationship between cigarette smoke and poor treatment-related outcomes in patients with TB is therefore questionable. We investigated whether constituents of tobacco smoke impair mycobacterial host immune responses in vitro.
  
  
  METHODS
  Preparation of a cigarette smoke extract (CSE) from Marlboro Red cigarettes was standardised and reproducibility verified by mass spectroscopy. Macrophages were derived from peripheral blood monocytes (MDM) and alveolar macrophages from bronchoalveolar lavage fluid from healthy non-smoking volunteers. Mycobacterial uptake (flow cytometric detection of fluorescence using green fluorescent protein-labelled BCG), cytokine responses (ELISA) and mycobacterial containment (colony forming units) was evaluated in both macrophage populations with and without co-culture with CSE, nicotine and a nicotine receptor blocker.
  
  
  RESULTS
  Cigarette smoke failed to impair the uptake of mycobacteria by monocyte-derived or alveolar macrophages. CSE (vs no CSE) reduced the mean (SD) BCG-driven macrophage (MDM) interferon γ (IFN-γ), tumour necrosis factor α (TNF-α) and interleukin 10 (IL-10) responses by 56.4 (18.6)%, 67.0 (33.4)% and 77.7 (27.7)%, respectively (p<0.001). Nicotine alone impaired IL-10 and TNF-α production by 48.8 (37)% and 49 (50)%, respectively (p<0.05) through an α-7 nicotine receptor-independent mechanism. In 5-day cultures, CSE impaired mycobacterial (BCG) containment in both monocyte-derived and alveolar macrophages.
  
  
  CONCLUSIONS
  Cigarette smoke attenuates effector cytokine responses and impairs mycobacterial containment within infected human macrophages derived from the peripheral blood and alveolar compartments, thus supporting the hypothesis that cigarette smoke subverts mycobacteria-related immunity.
authors.affiliation: Lung Infection and Immunity Unit, Division of Pulmonology & UCT Lung Institute, Department of Medicine, University of Cape Town, South Africa.
authors.forename: Richard N
authors.initials: RN
authors.lastname: van Zyl-Smit
authors.forename: Anke
authors.initials: A
authors.lastname: Binder
authors.forename: Richard
authors.initials: R
authors.lastname: Meldau
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Semple
authors.forename: Alicia
authors.initials: A
authors.lastname: Evans
authors.forename: Peter
authors.initials: P
authors.lastname: Smith
authors.forename: Eric D
authors.initials: ED
authors.lastname: Bateman
authors.forename: Keertan
authors.initials: K
authors.lastname: Dheda
mesh_terms: D001992:Bronchoalveolar Lavage Fluid; D016207:Cytokines / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology*; D016676:Macrophages, Alveolar / Q000378:metabolism / Q000382:microbiology*; D013058:Mass Spectrometry; D009163:Mycobacterium bovis / Q000472:pathogenicity*; D012906:Smoke / Q000009:adverse effects*; D014026:Nicotiana
chemical_list: D016207:Cytokines; D012906:Smoke
keywords: Respiratory Infection; Tobacco and the Lung; Tuberculosis