Figure 3. Maternal immunoglobulin-mediated imprinting of allergic responses in the offspring.
Maternal IgG (blue) to airborne allergens and food allergens reach the offspring in utero by a transfer across the placenta and after birth through breast milk and transfer across the gut. The neonatal Fc receptor (FcRn) carries maternal IgG either free or bound to allergen. Free IgG can inhibit allergic sensitisation in offspring by modulating B cell reactivity. Allergen-IgG immune complexes can induce immune tolerance by promoting allergen specific Treg expansion . Maternal IgE (purple) might also be transported across the placenta by FcRn. Fetal mast cells bear the IgE receptor (FcεR1) and bind maternal IgE. In mice, these IgE-loaded fetal mast cells are functionally competent, degranulate upon exposure to allergen, and persist in neonates, in whom they may mediate allergic disease in early life. Maternal secretary IgA (orange) are also found in human breast milk and might decrease allergic sensitisation by controlling allergen transfer across offspring gut. Evidence in mice also suggest they might control the expansion of Tregs in offspring.