Harmful brain inflammation triggered by a subset of immune cells can be quelled by the action of a hormone on an oestrogen receptor.

Microglia are immune cells that trigger inflammation in the central nervous system and carry an oestrogen receptor called ERβ. Christopher Glass and Kaoru Saijo at the University of California, San Diego, and their team screened a panel of molecules that bind to ERβ for their ability to block inflammation in microglia. They found that a few synthetic chemicals, as well as a natural steroid hormone called ADIOL, activate ERβ, kicking off a cascade of reactions that ultimately prevents inflammation. ADIOL also protects mice from an autoimmune condition similar to multiple sclerosis.

The authors suggest that drugs that stimulate this pathway could be used to treat neurodegenerative and autoimmune diseases.

Cell 145, 584–595 (2011)