Loibichler C, Pichler J, Gerstmayr M, et al. Clin Exp Allergy. 2002;32:1546–1551
Purpose of the Study.
The pre- and postnatal environment appears to be of crucial importance for the manifestation of allergic diseases that often begin in infancy. This study sought to determine if food and inhalant allergens are transported across placenta.
Placentas from 44 normal term pregnancies and from 4 preterm pregnancies (26, 28, 32, and 34 weeks of gestation) were investigated.
Placentas were obtained immediately after delivery to recover functionally active maternal and fetal circulation. A fetal artery and a fetal vein were cannulated and perfused with pure medium, whereas the intervillous space of placenta was flushed with allergen containing medium (materno-placental circulation). Samples were collected throughout the perfusion experiment from fetal venous outflow and tested for the presence of β-lactoglobulin (BLG), ovalbumin (OVA) and the inhalant birch pollen allergen Bet v 1.
Transplacental transfer of BLG, OVA, and Bet v 1 was detected in both term and premature placentas. The allergens were readily detectable in fetal effluent at the beginning of the perfusion experiment and allergen levels reached plateau after about 2 hours. The steady state transfer rate of BLG and OVA in term placentas was 0.012% ± 0.001 and 0.013% ± 0.001 of total dose. The observed transfer rate of Bet v 1 after 2 hours of perfusion was 0.155% ± 0.034 of total dose. Transplacentally transferred concentration of BLG and OVA in preterm placentas increased continuously throughout perfusion time.
Allergen-specific cord blood reactivity may be attributed to low levels of allergens crossing the human placenta and providing the fetus with the necessary stimulus for T cell priming.
An accumulating body of evidence supports the transplacental transfer of food and environmental allergens. Specific immunoglobulin (IgE) antibodies are present in the cord blood and furthermore, peripheral blood mononuclear cells from fetuses as early as 20 weeks of gestation proliferate on stimulation with specific allergens indicating previous exposure. Transplacental transfer of food allergens such as peanut may be partially responsible for early sensitization and development of food allergy.