Abstract
The present report discusses the immune and clearance system of the central nervous system (CNS) in terms of its anatomical, physiological, and biochemical properties. There is now a growing body of evidence that progressive dysfunction of the meningeal lymphatic system should be considered as a risk factor for aging-related brain disorders. In addition, the activity of meningeal lymphatics may alter the access of CSF-carried immune neuromodulators to brain parenchyma, which is also involved in the onset of aging and AD. In the CNS clearance system, impairment of the BBB and small arteries, as well as the major protein of the end feet of astrocytes, AQP4, are associated with aging or AD. The idea of maximizing brain "waste discharge" as a new preventive or therapeutic target for neurodegenerative diseases in the context of healthy aging has been accepted.