The C–C chemokine receptor 7: An immune molecule that modulates central nervous system function in homeostasis and disease

The interaction between the central nervous system (CNS) and the peripheral immune system is key for brain function in homeostasis and disease. Recent studies have revealed that the C–C chemokine receptor 7 (CCR7) is expressed in both CNS resident cells and peripheral immune cells, and plays an important role in regulating behavior in homeostasis and neuroinflammation in disease. This review integrates studies examining the role of CCR7 in CNS resident and peripheral immune cells in homeostasis and disease, as well as the pathways of peripheral immune cell migration in and out of the brain via CCR7. A special emphasis is placed on the CCR7-dependent migration of peripheral immune cells into the recently discovered meningeal lymphatic vessels surrounding the brain and nasal lymphatics, its migration into cervical lymph nodes, and the implications that this migration might have for CNS function.