Background The proliferation of cord blood mononulear cells in response to nutritive and inhalant allergens implies intrauterine exposure with resulting T cell priming. However, the mechanisms triggering these fetal allergen-specific immune responses are incompletely understood.
Methods We studied the placental release of endogenous β-lactoglobulin (BLG) and ovalbumin (OVA) by the use of an open ex vivo placental perfusion model. Preterm and term placentas were obtained immediately after delivery to recover functionally active fetal and maternal circulations. Fetal and maternal perfusate samples were collected throughout the perfusion experiments with medium. Matched cord blood samples were collected separately. All samples were tested for the presence of OVA and BLG by allergen-specific ELISAs.
Results In 16 out of 19 placentas, the nutritive allergens could be detected both in fetal and maternal perfusate samples. Fetal wash out levels of the allergens BLG and OVA from the placental tissue of preterm and term deliveries were observed in traces and up to 44.4 and 2.6 ng/mL, respectively. In cord blood of preterm and term neonates, BLG and OVA could be detected at concentrations up to 16.7 and 5 ng/mL, respectively.
Conclusion These findings provide direct evidence for the release of tiny amounts of nutritive allergens from placental tissue indicating diaplacental allergen transfer and fetal exposure to nutritive allergens in vivo.