Innate immune cells in healthy aging and Alzheimer's disease

Increasing evidence suggests that the immune system may play an important role in Alzheimer's disease. The most common immune cells in the brain are known as microglia. However, another type of immune cell, known as monocytes, which circulate throughout the body, can also enter the brain where they may influence disease development and progression. Microglia and monocytes can have both beneficial and harmful effects on the brain, but how their function is regulated is not well understood.