TSLP is expressed at human maternal-fetal interface in the early pregnancy. TSLP expression was evaluated by RT-PCR (A), immunohistochemistry (B), and immocytochemistry (C). Both villi and decidua from the early pregnancy and endometrial tissues from nonpregnant women expressed TSLP mRNA. The primary human trophoblasts (Tros), DECs, and DSCs also expressed TSLP mRNA (A). TSLP protein was localized in the cytoplasm of Tros (single arrow, cytotrophoblast cells; double arrow, syncytiotrophoblast cells) in villi and the cytoplasm of DECs (↑) in decidua (B), but absent in DSCs (▴). TSLP protein could not be detected in endometrium of the nonpregnancy, including proliferative and secretory phase (B). These results were further confirmed in the primary trophoblasts, DECs, and DSCs (C). Data are mean ± SD. The experiments were repeated 4 times with 4 placenta, decidua and endometrial tissue samples, respectively. The picture is a representative one.