A comprehensive review: neuroinflammation and immune communication between the central nervous system and the periphery

Immunity in the central nervous system (CNS) is generally attributed to neuron-associated microglia in the parenchyma. Microglial cells are specialized macrophages that interact closely with neurons to monitor them for signs of infection or injury. In addition to microglia, several other specialized macrophage populations are located at the borders of the CNS, including dural, leptomeningeal, perivascular, and choroid plexus macrophages. Collectively, these are CNS-associated macrophages (CAMs), but how these cells maintain the balance between the segregation of the CNS and the information transfer between the CNS parenchyma and the peripheral system is not well understood. The interaction between the immune system and the CNS is a newly emerging field of study that focuses on the functions of resident microglia and specialized macrophages, including leptomeningeal, choroid plexus, and perivascular macrophages. This review will help to improve understanding of the regulatory mechanisms of microglia and specialized macrophages and their involvement in the communication with the peripheral immune system. It could also advance neurological disease therapies that selectively target specific immune function parameters more effectively for managing neurodegenerative diseases.