Secondhand smoke exposure and serum cytokine levels in healthy children.
INTRODUCTION
Exposure to secondhand smoke (SHS) is associated with morbidity in children. Alterations in immune responses may explain this relationship, but have not been well-studied in children. Our objective was to determine the association between SHS exposure and serum cytokine levels in healthy children.


METHODS
We recruited 1-6 year old patients undergoing routine procedures. A parent interview assessed medical history and SHS exposure. Children with asthma were excluded. Blood was collected under anesthesia. We used Luminex Multiplex Assays to test for a panel of cytokines; cotinine was determined using an enzyme-linked immunosorbent assay. Children were categorized as no, intermediate, or high exposure. A mixed-effects model was fit to determine differences in cytokines by exposure level.


RESULTS
Of the 40 children recruited, 65% (N=26) had SHS exposure; 16 intermediate, and 10 high. There were no differences by demographics. In bivariate analyses, children exposed to SHS had lower concentrations of IL-1β, IL-4, IL-5, and IFN-γ than those with no exposure. In the mixed-effects model, children with any SHS exposure had significantly lower concentrations of IL-1β (0.554 pg/mL vs. 0.249 pg/mL) and IFN-γ (4.193 pg/mL vs. 0.816 pg/mL), and children with high exposure had significantly lower mean concentrations of IL-4 (8.141 pg/mL vs. 0.135 pg/mL) than children with no exposure.


CONCLUSIONS
This study suggests that SHS exposure decreases expression of some pro-inflammatory cytokines in SHS exposed children, including IFN-γ. Further research to describe the acute and chronic effects of SHS on the immune systems of children is needed.