Responses of Human Placental Choriocarcinoma Cells (BeWo) to Allergen is dependent on the dose and time of exposure

Krishna Bimal R, Qureshi Mahboob, Patel Ricky, Durre Kainath. Touro University Nevada, Pharmacology 89074, USA.

Trans-placental transfer of various allergens has been described to cause an antigen-specific immune response at the maternal-fetal interphase. The effects of these allergens have yet to be understood in regards to proliferation of syncytiotrophoblasts residing on the external surface of the placenta and their cytokine responses. Dose dependent cellular proliferation in response to ovalbumin was examined on human placental choriocarcinoma (BeWo) cells in terms of cellular proliferation and cytokine responses. Microscopic images of the choriocarcinoma cell cultures were taken at 36-hour intervals to examine the cellular proliferation response to ovalbumin (1 ng/ml- 10 µg/ml; with a 10-fold increase). The numbers of replicating cellular units were counted per 10 microscopic fields; and, a total cell count was taken at the end of the 108-hour time period. There was an increase in the number of replicating cellular units in the ovalbumin treated groups (remarkable at 100ng and 1µg). It has been shown in previous studies that TGF-β plays a critical role in the materno-fetal interphase to maintain pregnancy. After 36-hours of primary exposure at low dose of ovalbumin, ELISA revealed a decreased production of TGF-β; however, these cells were able to recover their TGF-β production once ovalbumin was discontinued at 72-hours. In the ovalbumin treated groups of 100ng and 10µg, reduced TGF-β production was observed upon re-exposure at 36-hours. At these high concentrations of ovalbumin, a delayed inhibition of TGF-β production occurs only after re-exposure to the allergen.

These findings suggest that placental function and integrity will likely be maintained upon low dose exposure to the allergen. Sustained exposure to high doses of ovalbumin prevents the recovery in TGF-β production which may prove to be detrimental to placental function, as adequate levels of TGF-β is critical for ensuring a favorable environment at the materno-fetal interphase during pregnancy.