Hormone wards off immune cells in womb

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. Yet in most pregnant

women, embryos are spared by a poorly understood mechanism that holds her immune

cells at bay.

Earlier research suggested that the interaction between proteins called Fas and

Fas ligand (FasL) keeps potentially dangerous maternal immune cells safely away

from the embryo (SN: 6/14/97, p. 371). Fas resides on the surface of immune cells