Localizing central nervous system immune surveillance: Meningeal antigen‐presenting cells activate T cells during experimental autoimmune encephalomyelitis

The onset of neurological signs in experimental autoimmune encephalomyelitis is tightly associated with infiltration and reactivation of T cells in the central nervous system. The anatomic localization of the initial T cell‐antigen‐presenting cell (APC) interactions leading to reactivation of T cells in the central nervous system is, however, still unclear. We hypothesized that activated CD4+ T cells gain direct access to the subarachnoid space and become reactivated on encounter with cognate antigen in this compartment.