Alveolar Macrophage from Cigarette Smoke-Exposed Mice Inhibits B Lymphocyte Proliferation Stimulated with LPS

Background: Smokers have higher incidences of pulmonary diseases. This increased susceptibility may result from cigarette smoke (CS)-induced impairment of the pulmonary immune system. However, the mechanism(s) is not fully understood. Objective: The aim of this study was to investigate the mechanism of the effect of alveolar macrophages (AM) from CS-exposed mice on B lymphocyte proliferation stimulated with bacterial lipopolysaccharide (LPS). Methods: Mice were exposed to CS using a Hamburg smoking machine, and AM were obtained by bronchoalveolar lavage. Lymphocytes were harvested from spleen in normal mice. AM-mediated B lymphocyte proliferation stimulated with LPS was assessed by the 3 H-thymidine method, using lymphocytes as responding cells and AM from CS-exposed or non-CS-exposed mice. Generations of superoxide and hydrogen peroxide were analyzed by flow cytometory, using hydroethidine and dichlorofluorescein diacetate. Results: AM from CS-exposed mice significantly inhibited B lymphocyte proliferation stimulated with LPS compared with AM from non-CS-exposed mice. Generations of superoxide and hydrogen peroxide were significantly increased in CS-exposed AM compared with non-CS-exposed AM. Inhibition of B lymphocyte proliferation stimulated with LPS by AM from CS-exposed mice was clearly recovered by superoxide dismutase and catalase. Conclusions: These results suggest that the inhibition by CS-exposed AM of LPS-induced B lymphocyte proliferation may be caused by the increased superoxide and hydrogen peroxide generation of CS. Therefore, these immunological inhibitions by CS could be associated with increased risk of pulmonary diseases.