Role of CCR2 in immunobiology and neurobiology

Chemokines and their receptors play crucial roles in the trafficking of leukocytes and are of particular interest in the context of the unique inflammatory responses elicited in the central nervous system (CNS). The chemokine receptor CCR2 and its ligand CCL2 have been implicated in a wide range of immunobiological processes and neuropathologies, including recruitment of monocytes and regulation of bone marrow homeostasis, as well as multiple sclerosis, HIV-associated dementia, Alzheimer's disease and neuropathic pain. Recently, powerful biological tools (CCR2-red fluorescent protein [RFP] knock-in mice) have been developed to analyze the functions of CCR2 in different cell populations, and intriguing results have emerged from those mice. The present review emphasizes CCR2/CCL2 as a key chemokine/chemokine receptor pair that controls the recruitment or retention of a key subset of mononuclear phagocytes in inflammation associated with host defense or disease.