Perivascular macrophages proliferate in the CNS, but also contributed by bone-marrow precursors in response to cerebral ischemia

Immune response following CNS disease and injury comprises three different compartments, parenchymal, perivascular and blood involving specialized immune cells. Microglia are the major immune cell residing in the CNS parenchymal compartment but together with other macrophages which are residing in the non-parenchymal structures such as perivascular spaces, leptomeninges and choroid plexus constitute the total macrophage population of the CNS. While the homeostatic functions of these specialized macrophages in not very well understood, evidence shows that these macrophages at the blood-brain interface might involve immune-surveillance and establish a gate way for the recruitment of peripheral immune cells in to the CNS in response to the pathological stimuli. In humans and rats these macrophages identified exclusively by the high levels of scavenger receptor CD163