Dendritic cells in brain diseases.

Dendritic cells (DCs) are professional antigen presenting cells that constantly survey the environment acting as sentinels of the immune system, including in the CNS. DCs are strategically located near the cerebrospinal fluid, but they can potentially migrate to draining cervical lymph nodes either triggering immunogenic T cell responses or displaying tolerogenic functions. Under physiological conditions, the presence of DCs in the brain parenchyma is minimal but their numbers increase in neuroinflammation. Although DCs belong to a distinct immune cell lineage, they show various phenotypes and share certain common markers with monocytes, macrophages, and microglia. All these cells can express major histocompatibility complex class II, and acquire similar morphologies hampering their precise identification. Neuroinflammation is increasingly recognized in many brain disorders; here we review the literature reporting DCs in the inflamed brain in disease conditions and corresponding animal models of multiple sclerosis, stroke, brain tumors, Alzheimer's disease, Parkinson's disease, and epilepsy.