Dose-Dependent and Preterm- Accentuated Diaplacental Transport of Nutritive Allergens in vitro

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Objective: The mechanisms by which nutritive allergens are transported from mother to fetus and the ensuing immunological response are incompletely understood. We investigated the role of different allergen concentrations in influencing the diaplacental allergen transport in preterm and term placentas. Method: Twenty-seven human term placentas and 12 preterm placentas were dually perfused in vitrofor up to 4 h by adding alternately two different nutritive allergens, β-lactoglobulin (BLG) or ovalbumin (OVA), at four different allergen concentrations (0.02, 0.2, 2 and 20 mg/ml) to the maternal perfusate medium. Allergen concentrations in fetal venous outflow samples collected during perfusion were measured by using specific ELISAs. Results: Perfusion of increasing allergen concentrations via the maternal circulation resulted in a concentration-dependent increase of fetal allergen uptake in all term and preterm placentas. A mean maternal-to-fetal ratio of 20,000/1 and 3,000/1 for BLG, and 40,000/1 and 5,000/1 for OVA was found in term and preterm placentas, respectively. Preterm placentas (27–36 weeks of gestation) were found to favor the diaplacental passage of nutritive allergens compared with placentas at term (>36 weeks of gestation). Conclusion: Maternal-to-fetal allergen transport occurs in a dose-dependent and molecular weight-dependent manner with clear accentuation in preterm placentas.