title: IgG transmitted from allergic mothers decreases allergic sensitization in breastfed offspring.
abstract: BACKGROUND
  The mechanism(s) responsible for the reduced risk of allergic disease in breastfed infants are not fully understood. Using an established murine model of asthma, we demonstrated previously that resistance to allergic airway disease transmitted from allergic mothers to breastfed offspring requires maternal B cell-derived factors.
  
  
  OBJECTIVE
  The aim of this study was to investigate the role of offspring neonatal Fc receptor for IgG uptake by intestinal epithelial cells (FcRn) in this breast milk transferred protection from allergy.
  
  
  METHODS
  Allergic airway disease was induced during pregnancy in C57BL/6 female mice. These allergic mothers foster nursed naive FcRn+/- or FcRn-/- progeny born to FcRn+/- females that were mated to C57BL/6J-FcRn-/- male mice. In offspring deficient in FcRn, we expected reduced levels of systemic allergen-specific IgG1, a consequence of decreased absorption of maternal IgG from the lumen of the neonatal gastrointestinal tract. Using this model, we were able to investigate how breast milk IgG affected offspring responses to allergic sensitization.
  
  
  RESULTS
  Levels of maternal antibodies absorbed from the breast milk of allergic foster mothers were determined in weanling FcRn-sufficient or -deficient mice. Maternal transmission of allergen-specific IgG1 to breastfed FcRn-/- offspring was at levels 103-104 lower than observed in FcRn+/- or FcRn+/+ mice. Five weeks after weaning, when offspring were 8 wk old, mice were sensitized and challenged to evaluate their susceptibility to develop allergic airway disease. Protection, indicated by reduced parameters of disease (allergen-specific IgE in serum, eosinophilic inflammation in the airways and lung) were evident in FcRn-sufficient mice nursed as neonates by allergic mothers. In contrast, FcRn-deficient mice breastfed by the same mothers acquired limited, if any, protection from development of allergen-specific IgE and associated pathology.
  
  
  CONCLUSIONS
  FcRn expression was a major factor in determining how breastfed offspring of allergic mothers acquired levels of systemic allergen-specific IgG1 sufficient to inhibit allergic sensitization in this model.
authors.affiliation: Department of Immunology, University of Connecticut Health Center, Farmington, Connecticut, USA. puddington@nso1.uchc.edu.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Matson
authors.forename: Roger S
authors.initials: RS
authors.lastname: Thrall
authors.forename: Ektor
authors.initials: E
authors.lastname: Rafti
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Lingenheld
authors.forename: Lynn
authors.initials: L
authors.lastname: Puddington