Maternal Tobacco Smoking and Decreased Leukocytes, Including Dendritic Cells, in Neonates

Abstract

Maternal smoking in pregnancy is associated with respiratory diseases in the offspring, possibly due to prenatal influences on the developing immune system. We investigated whether maternal smoking in pregnancy was associated with cord blood leukocyte numbers, including precursor dendritic cells, adjusting for concomitant factors. In a prospective healthy birth cohort study, total leukocyte counts were reduced in neonates of smoking mothers [10.7 (8.4 -13.0 E nvironmental tobacco smoke exposure is associated with an increased risk of infections, impaired lung development, and respiratory morbidity and mortality in children (1). Specifically, smoking during pregnancy has been shown to act as an independent risk factor for wheezing disorders when compared with postnatal exposure to environmental tobacco smoke (2). Whereas inhaled tobacco smoke is known to have an effect on leukocyte numbers in the blood and to induce inflammatory responses in the airways of human adults, the effects of maternal smoking on blood counts and early immune responses of the offspring are poorly understood.Studies showing a decrease in leukocyte counts, especially neutrophilic granulocytes, in cord blood of neonates of smoking mothers have lead to the conclusion that this decrease might contribute to the susceptibility to infections and therefore increased respiratory morbidity in these children (3,4). However, these studies used only univariate statistical methods and were therefore not able to determine whether the decreased leukocyte counts were independently associated with maternal smoking, or whether they could be explained by other factors (e.g. maternal age or perinatal stress) that might be associated with both, maternal smoking and neonatal cell counts.The decrease in the number of neutrophilic granulocytes might contribute to an increased susceptibility to bacterial infections, whereas it is unlikely to be the major cause for the increased susceptibility to viral infections that are associated with symptoms of wheeze. Not neutrophils but other leukocytes such as lymphocytes and antigen-presenting dendritic cells play a more important role in the defense against most viral infections. Dysregulation of these cells may furthermore contribute to the development of allergy and asthma (5,6). Nicotine, one of the main constituents of cigarette smoke, has a suppressive effect on myeloid dendritic cells (7-9). As a consequence, these cells may be particularly affected in children of smoking mothers.The aim of this study was to investigate whether maternal smoking in pregnancy was associated with a decrease of lymphocytes and dendritic precursor cells in the cord blood of the neonates and whether these differences in leukocyte subtypes remained after adjustment for other determinants of neonatal leukocyte counts, such as maternal age, infections, atopic diseases, and perinatal stress. MATERIALS AND METHODSSubjects and protocol. In a prospective birth cohort study, 97 Caucasian infants were prenatally recruited from seven mat...

Exposure to Moderate Air Pollution during Late Pregnancy and Cord Blood Cytokine Secretion in Healthy Neonates

“…In line with our results one recent study found lower IL-6 and IL-10 responses to toll like receptor-2 ligation in cord blood of infants from smoking mothers [24]. Another study found decreased leukocyte subsets including myeloid precursor dendritic cells in cord blood of smoking mothers [13]. Also in parallel to our results, Hertz-Picciotto et al have examined associations between air pollution and lymphocyte immunophenotypes in cord blood among 1397 deliveries in the Czech Republic.…”

“…While distinct environmental exposure in utero such as microbial stimuli may be protective for the development of allergic diseases in childhood via specific immune regulatory mechanisms [8], [10], exposure to air pollution was shown to be associated with an increase in allergic diseases [11]. Indeed, first evidence indicates influences on cord blood immune responses such as a change in relative distribution of lymphocytes by exposure to low ambient air pollution or if mothers smoked during pregnancy [12], [13].…”

Association of Maternal Smoking During Pregnancy With Infant Hospitalization and Mortality Due to Infectious Diseases

“…This again suggests an alternative causal mechanism, and an adverse effect of in utero smoke exposure on the infant immune system is a plausible explanation. Studies analyzing cord-blood of infants (29–31) and exposure of primates (32) have shown that infant immune systems can be modified by exposure to tobacco smoke; however, further research is needed to understand the biological mechanisms for this.…”

Childhood socioeconomic factors and perinatal characteristics influence development of rheumatoid arthritis in adulthood

“…Prenatal maternal smoking29 and early postnatal exposure to second-hand smoke30 can affect the neonatal and developing immune function. Maternal smoking in pregnancy was associated with childhood RA in one study,10 but another large study reported no association with living with a parent who smoked 19.…”