Expression of Estrogen Receptors in Main Immune Organs in Sheep During Early Pregnancy

Estrogen exerts its action via estrogen receptors (ERs), including ERα and ERβ, and has effects on immunomodulation during pregnancy. It is known that there are changes in the function of the maternal immune organs during pregnancy. However, it is not clear if early pregnancy has effects on the expression of ERα and ERβ in the ovine maternal thymus, lymph nodes, spleen, and liver. In this study, these maternal immune organs were harvested at day 16 of the estrous cycle and at days 13, 16, and 25 of pregnancy (n = 6 for each group) after the ewes were euthanized. The mRNA and protein expression of ERα and ERβ were analyzed using real-time PCR and Western blot and immunohistochemical analyses. The results reveal that the mRNA and protein expression of both ERα and ERβ were upregulated in the maternal spleen and the expression of ERα and ERβ in the thymus, lymph nodes, and liver was modulated during early pregnancy. In conclusion, early pregnancy modulates the expression of ERα and ERβ in the maternal thymus, lymph nodes, spleen, and liver in a tissue-specific manner, which is related to the regulation of maternal immune function during early pregnancy in ewes.