Acute effects of smoking and high experimental exposure to environmental tobacco smoke (ETS) on the immune system

Abstract

Controversial results have been published on the immune response to cigarette smoking while the effects of exposure to environmental tobacco smoke (ETS) have not yet been reported. In a controlled study, acute effects of smoking and of a high environmental exposure to ETS on immunological parameters have been investigated. The study consisted of four experimental days, two control and two exposure days. On control days, 1 and 3, smokers (n=5) and nonsmokers (n=5) sat in an unventilated 45 m³ room for 8 h. On the exposure days, 2 and 4, each of the smokers smoked 24 cigarettes in 8 h, while the nonsmokers were exposed to the ETS generated by the smoking volunteers. Blood was drawn before and after each exposure session on all four experimental days for dosimetry of tobacco smoke exposure and determination of the immune response. Flow cytometry using monoclonal antibodies was used to determine CD3⁺ cells (whole T cells), CD19⁺ cells (B lymphocytes), CD16⁺ and CD56⁺ cells (natural killer cells), CD4⁺ cells (T-helper cells), CD8⁺ cells (T-suppressor cells), the CD4⁺/CD8⁺ (helper/supressor ratio), and Fc receptors on granulocytes. Serum was analyzed for soluble CD14 receptors (scD14), interleukin 1, interleukin 6 and prostaglandin E₂ (PGE₂). Functional stimulation assays were performed to determine the basal and induced level of reactive oxygen intermediate (ROI) production by polymorphic neutrophils. Exposure to tobacco smoke in both groups was confirmed by dosimetry of carboxyhemoglobin, plasma nicotine, and cotinine levels. In comparison to nonsmokers, smokers had elevated granulocyte cell counts, increased CD16⁺ and CD56⁺ cell levels and decreased CD3⁺ and CD19⁺ levels. Acute smoking, but not exposure to ETS, resulted in a slight decrease in the number of CD19⁺ cells and an increase in the number of granulocytes; the latter was restricted to one subject. Acute smoking and exposure to high experimental concentrations of ETS resulted in a slight increase in CD16⁺ and CD56⁺ cells. None of the changes determined in immunological parameters after either acute smoking or exposure to ETS reached statistical significance. Serum sCD14, cytokine and PGE₂, functional stimulation of in vitro ROI production, and changes in Fc receptors were not affected by acute smoking or exposure to ETS. Although no clear guidelines exist to assess immunotoxicity in man, our data do not favor immunosuppression and the possibility of increased risk of infection in nonsmokers exposed to ETS under real-life conditions.