title: Mode of delivery and cord blood cytokines: a birth cohort study.
abstract: BACKGROUND
  The mechanisms for the association between birth by cesarean section and atopy and asthma are largely unknown.
  
  
  OBJECTIVE
  To examine whether cesarean section results in neonatal secretion of cytokines that are associated with increased risk of atopy and/or asthma in childhood. To examine whether the association between mode of delivery and neonatal immune responses is explained by exposure to the maternal gut flora (a marker of the vaginal flora).
  
  
  METHODS
  CBMCs were isolated from 37 neonates at delivery, and secretion of IL-13, IFN-gamma, and IL-10 (at baseline and after stimulation with antigens [dust mite and cat dander allergens, phytohemagglutinin, and lipopolysaccharide]) was quantified by ELISA. Total and specific microbes were quantified in maternal stool. The relation between mode of delivery and cord blood cytokines was examined by linear regression. The relation between maternal stool microbes and cord blood cytokines was examined by Spearman's correlation coefficients.
  
  
  RESULTS
  Cesarean section was associated with increased levels of IL-13 and IFN-gamma. In multivariate analyses, cesarean section was associated with an increment of 79.4 pg/ml in secretion of IL-13 by CBMCs after stimulation with dust mite allergen (P < 0.001). Among children born by vaginal delivery, gram-positive anaerobes and total anaerobes in maternal stool were positively correlated with levels of IL-10, and gram-negative aerobic bacteria in maternal stool were negatively correlated with levels of IL-13 and IFN-gamma.
  
  
  CONCLUSIONS
  Cesarean section is associated with increased levels of IL-13 and IFN-gamma, perhaps because of lack of labor and/or reduced exposure to specific microbes (e.g., gram-positive anaerobes) at birth.
authors.affiliation: Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA. ngoc.ly@channing.harvard.edu
authors.forename: Ngoc P
authors.initials: NP
authors.lastname: Ly
authors.forename: Begoña
authors.initials: B
authors.lastname: Ruiz-Pérez
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Onderdonk
authors.forename: Arthur O
authors.initials: AO
authors.lastname: Tzianabos
authors.forename: Augusto A
authors.initials: AA
authors.lastname: Litonjua
authors.forename: Catherine
authors.initials: C
authors.lastname: Liang
authors.forename: Daniel
authors.initials: D
authors.lastname: Laskey
authors.forename: Mary L
authors.initials: ML
authors.lastname: Delaney
authors.forename: Andrea M
authors.initials: AM
authors.lastname: DuBois
authors.forename: Hara
authors.initials: H
authors.lastname: Levy
authors.forename: Diane R
authors.initials: DR
authors.lastname: Gold
authors.forename: Louise M
authors.initials: LM
authors.lastname: Ryan
authors.forename: Scott T
authors.initials: ST
authors.lastname: Weiss
authors.forename: Juan C
authors.initials: JC
authors.lastname: Celedón