News Health & Medicine Hormone wards off immune cells in womb By Ben Harder October 17, 2001 at 2:43 pm - More than 2 years ago Share this:Share Share via email (Opens in new window) Email Share on Facebook (Opens in new window) Facebook Share on Reddit (Opens in new window) Reddit Share on X (Opens in new window) X Print (Opens in new window) Print A hormone known for its involvement in the brain’s response to stress also plays a key role in shielding the developing embryo from its mother’s immune system. In its newly identified function, corticotropin-releasing hormone (CRH) stimulates the production of a protein previously found to prevent maternal immune cells from attacking embryonic tissue. The immune system is primed to reject any cells, even those of an embryo, that display an immune chemistry distinct from their host’s.