Corticotrophin-releasing hormone (CRH) participates in the implantation of embryos and early pregnancy tolerance via pathways that remain poorly understood. In October Nature Immunology, Makrigiannakis and colleagues from University of Crete School of Medicine, Greece, show that locally produced embryonic and endometrial CRH promotes implantation and maintenance of early pregnancy primarily by killing activated T cells.

Makrigiannakis et al. studied isolated primary human extravillous trophoblast cells and found that antalarmin, a CRH receptor type 1 antagonist, decreased FasL expression and promoted apoptosis of activated T lymphocytes, an effect potentiated by CRH. In addition, they found that female rats treated with antalarmin had a reduced number of successful pregnancies and a diminished endometrial FasL expression, whilst antalarmin treated mothers that lacked T cells did not reject the embryos (Nat Immunol 2001, DOI: 10.1038/ni722).

These results suggest a potential cause of female infertility and may also lead to the...