Direct evidence for transplacental allergen transfer

Allergies are increasing, and despite deeper insights into the immunologic basis of these diseases, preventive measures are not yet efficient. As the induction of allergic diseases is often triggered in early childhood, perin atal or prenatal preventive strategies would be beneficial. We investigated the transfer of inhalant and nutritive allergens across the human placenta . For this purpose, the maternal side of a placental cotyledon was perfused in vitro with an allergen-containing medium, and a specific ELISA was used to detect the allergens on the fetal side. Both allergens evaluated, birch pollen major allergen Bet vl and the milk allergen beta-lactoglobulin, cou ld be shown to cross the placenta. The nutritive allergen beta-lactoglobuli n was not only transferred across the placenta in all eight experiments, bu t was also detectable within the first minutes of perfusion. The peak aller gen concentration on the fetal side could be increased by addition of human immunoglobulin. Far the inhalant allergen Bet v1, transfer was observed in two of 10 placental experiments, and only if human immunoglobulin was adde d. a pulsatility wave with a frequency of 30-35 min suggested tin active tr ansfer mechanism We conclude that allergens are actively and selectively tr ansferred across the placenta. Therefore, controlled maternal allergen expo sure might offer new ways to induce tolerance to specific allergens in the fetus.