The choroid plexus: both a gatekeeper and a conductor of neuroimmune communication.

The choroid plexus (ChP) is increasingly recognized as a dynamic neuroimmune interface that integrates peripheral and central signals to regulate cerebrospinal fluid (CSF) homeostasis, leukocyte trafficking, and inflammatory tone within the central nervous system (CNS). Recent studies reveal that beyond their classic roles in CSF production and barrier function, ChP epithelial cells are conductors of neuroimmune communication, actively remodeling the state of immune activity, immunosurveillance and responsiveness of immune cells in the CSF in response to infection, injury, malignancy, aging, and neurocognitive decline. Here, we review emerging evidence establishing the ChP in this role. We discuss resident immune cell function, mechanisms of pathogen and tumor cell entry, and ChP-mediated responses across disease states. Together, these findings establish the ChP as a central regulator of CNS immunity and a potential therapeutic target in neuroinflammation, CNS metastasis, and neurodegeneration.