 Interferons are known to be important for immune system function, but they have recently been found to play a key role in stem cell function as well. This research shows that interferons can both promote and suppress stem cell activity depending on the age of the organism. In younger brains, interferons help maintain stem cell activity, while in older brains, they reduce the ability of stem cells to activate. This suggests that interferons may be a promising therapeutic target for treating diseases associated with aging such as Alzheimer's disease. This article was authored by Damian Kava-Hullabonyas, Maxim Skapkin, Jua Huli, and others.