Found in cows and sheep, Interferon tau is the signal from the developing embryo to the mother that she is pregnant. It is secreted by the trophoblast cells into the uterine lumen in days 13-21 of pregnancy. It decreases endometrial oxytocin receptors, which then cannot stimulate PGF-2-alpha synthesis, preventing luteolysis. It promotes uterine implantation by increasing protein synthesis in glands.

References

• Bagnell, C. 2005. "Animal Reproduction". Rutgers University Department of Animal Sciences.