Novel insights into the origin and development of CNS macrophage subsets.

The central nervous system (CNS) hosts a variety of immune cells, including two distinct macrophage populations: microglia are found in the parenchyma, whereas CNS-associated macrophages (CAMs) cover the CNS interfaces, such as the perivascular spaces, the meninges and the choroid plexus. Recent studies have given novel insights into the nature of CAMs as compared to microglia. In this mini-review, we summarise the current knowledge about the ontogenetic relationship and the underlying mechanism for the establishment of CNS macrophages during development.