Maternal allergen-specific IgG may protect the child against allergic sensitization https://doi.org/10.1016/j.jaci.2018.11.051 Abstract: Abstract Background The analysis of allergen-specific IgE responses in birth cohorts with micro-arrayed allergens has provided detailed information regarding the evolution of specific IgE responses in children. High resolution data regarding early development of allergen-specific IgG are needed. Objective To analyze IgG reactivity to micro-arrayed allergens in mothers during pregnancy, in cord blood samples, breast milk and in infants in the first years of life with the aim to investigate if maternal allergen-specific IgG may protect against IgE sensitization in the offspring. Methods Plasma samples from mothers during third trimester, cord blood, breast milk collected at 2 months after delivery, and plasma samples from children at 6, 12 and 60 months of age were analyzed for IgG reactivity to 164 micro-arrayed allergens (ImmunoCAP ISAC technology) in 99 families in the Swedish birth cohort ALADDIN. IgE sensitizations to micro-arrayed allergens were determined at 5 years of age in the children. Results Allergen-specific IgG reactivity profiles in mothers, cord blood and breast milk were highly correlated. Maternal allergen-specific IgG persisted in some children at 6 months. Children′s allergen-specific IgG production occurred at 6 months and reflected allergen exposure. Children who were IgE-sensitized against an allergen at 5 years of age had significantly higher allergen-specific IgG levels than non-sensitized children. For all 164 tested allergens, children from mothers with elevated (>30 ISU) specific plasma IgG against an allergen had no IgE sensitizations against that allergen at 5 years of age. Conclusion This is the first detailed analysis of the molecular IgG recognition profile in mothers and their children in early life. High allergen-specific IgG reactivity in mother′s plasma and breast milk and in cord blood seemed to protect against allergic sensitization at 5 years of age. Clinical implication High levels of allergen-specific IgG in mothers during third trimester and in cord blood seem to protect against allergic sensitization in the offsprings. This finding has implications for the prevention of allergy. All Authors: lChristianLupinekMDa+HeidrunHochwallnerPhDa+CatharinaJohanssonPhDbAxelMiePhDbEvaRiglerMD, PhDaAnnikaScheyniusMD, PhDbcJohanAlmMD, PhDbcRudolfValentaMDade