Scientists found a surprising driver of Alzheimer’s outside the brain

Immune cells that usually defend the body by attacking infected or foreign cells appear in unusually high numbers in the brains of people with Alzheimer's disease and related conditions. Evidence suggests these cells contribute to neurodegeneration, but researchers have not known where they originate or what prompts them to gather in the brain.

A new study from Washington University School of Medicine in St. Louis points to an unexpected source outside the brain. In experiments with mice, researchers found that T cells receive signals from lymph nodes that appear to prepare them to enter the brain and contribute to damage. When the scientists disrupted those signals, neurodegeneration was dramatically reduced.

The findings reveal a previously unrecognized immune pathway that may offer a way to slow or potentially halt damage associated with Alzheimer's disease and primary tauopathies. These disorders are marked by twisted accumulations of tau protein in the brain.