There’s a small fire isolated in your kitchen. If you had the right tool, you might be able to put it out. But before you can, the sprinklers turn on and flood your entire house. An automatic response to an issue has now damaged everything you own.

That’s akin to what happens in the brains of people with Alzheimer’s: Amyloid plaques, sticky protein clumps that build up in the brain, are the fire in the kitchen. Microglia, the brain’s resident immune cells, are the sprinklers. A mechanism designed to protect the body ends up hurting it.

Researchers at the University of Kentucky have discovered this harmful process for the first time—and figured out how to turn it off.