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 cytometry, 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.