Regulation of Innate Immune Pathways

Cells must regulate their innate immune pathways so that they can respond rapidly to pathogens, yet avoid aberrant activation that can lead to inflammation. The evolution of these regulatory mechanisms remain to be understood, however. Elde, Feschotte and colleagues demonstrated that endogenous retroviruses, and the promoters that they introduce into the genome, have been co-opted by cells to play key roles in regulating the innate immune system. Although these regulatory sequences likely arose in ancient viruses, they now constitute a dynamic reservoir of interferon-inducible enhancers that fuel genetic innovation in mammalian immune defenses. Thus, we have turned the tables, and ancient viral DNA has now become important for mounting a proper defense against today's viral infections.