OBJECTIVES. Environmental tobacco smoke is associated with several negative health outcomes in children, including an increased susceptibility to infections. One of the postulated mechanisms for these effects is the impairment of the immune system function and/or development. Yet, it remains unknown whether cumulative exposure to parental smoking is associated with altered immune responses in childhood and whether these effects are independent of in utero exposure to maternal smoking. In a population-based birth cohort, we sought to determine the relation of parental smoking, as assessed prospectively since pregnancy, to the child's interferon γ and interleukin 4 production at 11 years of age.

PATIENTS AND METHODS. We used data on 512 children and their parents from the Tucson Children's Respiratory Study cohort. Information on maternal and paternal smoking was collected prospectively by questionnaire, and pack-years for mother, father, and both parents combined were assessed prospectively between the prenatal period and year 11. At age 11 years, children's interferon γ and interleukin 4 production from mitogen-stimulated peripheral blood mononuclear cells was measured.

RESULTS. Children of parents who smoked between the prenatal period and year 11 were more likely to be in lower quartiles of interferon γ production than children of nonsmoking parents. In addition, maternal, paternal, and parental pack-years showed significant inverse dose-response relationships with interferon γ production in the child. These dose-response relationships with interferon γ remained significant for both paternal and parental pack-years among children of mothers who did not smoke during pregnancy, suggesting the existence of specific postnatal effects of environmental tobacco smoke exposure. In contrast, no significant effects of parental smoking were found on interleukin 4 production.

CONCLUSIONS. Interferon γ responses of school-aged children are impacted by parental smoking.

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