Immune regulatory mechanisms influence early pathology in spinal cord injury and in spontaneous autoimmune encephalomyelitis

Injuries to the central nervous system (CNS) trigger an inflammatory reaction with potentially devastating consequences. In this report we compared the characteristics of the inflammatory response on spinal cord injury (SCI) caused by a stab wound between the T7 and T9 vertebrae and spontaneous experimental autoimmune encephalomyelitis (EAE). SCI and EAE were compared in two types of myelin basic protein Ac1-11-specific T-cell receptor transgenic mice: T/R⁺ mice harbor regulatory T cells, and T/R^- mice lack regulatory T cells. Our results show that 8 days after SCI, T/R^- mice developed a strong T-cell infiltrate in the spinal cord, with remarkable down-modulation of CD4 expression that was accompanied by a local increase in Mac-3⁺ and F4/80⁺ reactivity and diffuse local and distal astrogliosis. In contrast, T/R⁺ mice exhibited a modest increase in CD4⁺ cells localized to the site of injury, without CD4 down-modulation; focal astrogliosis was restricted to the site of the lesion, although Mac-3⁺ and F4/80⁺ cells were also present. Similarly to T/R^- mice that underwent SCI, T cells displaying down-modulated CD4 expression were found in the CNS of older T/R^- mice afflicted by spontaneous EAE. Overall, our results suggest that common mechanisms regulate T-cell accumulation in CNS lesions of different causes, such as mechanic lesion or autoimmune-mediated damage.