Scientists here report on a mechanism that might explain some fraction of the rising levels of chronic inflammation observed in the aging brain – though as in most such research, it is a proximate cause, and it isn’t very clear as to how it relates to the known root causes of aging. Whatever that relationship might be, it is clear enough that with advancing age the immune system falls into a state of continual, inappropriate activation and inflammation. This disrupts many important processes in the normal maintenance of tissue function, and particularly so in the brain, where immune cells undertake a greater range of important activities than is the case elsewhere in the body.
The activity of microglial cells plays an important role in brain aging. These cells are part of the brain’s immune defense: For example, they detect and digest bacteria, but also eliminate diseased or defective nerve cells. They also use messenger substances to alert other defense cells and thus initiate a concerted campaign to protect the brain: an inflammation. This protective mechanism has undesirable side effects; it can also cause damage to healthy brain tissue. Inflammations are therefore