The role of immune cells in brain development and neurodevelopmental diseases.

During brain development, the generation of neurons and glial cells is rigorously regulated by diverse mechanisms including the immune system. Dysfunction of the developing system results in the onset of neurodevelopmental disorders and psychological disorders. Recent studies have demonstrated that the immune system is implicated in brain development. As the central nervous system is physically separated from the circulatory system by the blood-brain barrier, circulating immune cells are unable to infiltrate into the brain parenchyma. However, several studies have demonstrated that immune cells, such as B cells, T cells and macrophages, are observed in the meningeal space, perivascular space and choroid plexus and have crucial roles in brain function. Moreover, genome-wide association studies have revealed that the immune system is implicated in neurodevelopmental disorders and psychological disorders. Here, we discuss the role of each of these immune cell types in brain development and the association with neurodevelopmental disorders.