Concept of autoimmunity following spinal cord injury: possible roles for T lymphocytes in the traumatized central nervous system.

The effect of immunological activation on the neuropathologic sequelae and neurologic outcome from spinal cord injury is unclear. Similar to models of neuroinflammatory disease (e.g., experimental autoimmune encephalomyelitis; EAE), injury to the spinal cord precipitates the activation of resident microglia and the recruitment of circulating inflammatory cells (e.g., macrophages and lymphocytes). In EAE, these cells are known to cause tissue damage and loss of neurological function via autoimmune reactions to myelin proteins. The role these cells play in the pathology of traumatic injury to the spinal cord has not been clarified. In this review, data are presented that indicate that T cells isolated from spinal-injured rats are capable of causing neurologic deficits and histopathologic changes similar to EAE when injected intravenously into naive animals. These data are consistent with the concept of trauma-induced autoimmune reactions. However, disease transfer was only possible when T cells were obtained from animals at 1 week post-injury. Thus, the encephalitogenic T-cell repertoire appears to be rapidly regulated. It is possible that trauma-induced autoimmunity evolves into a mechanism by which the autoreactive repertoire regulates ongoing central nervous system (CNS) immunologic responses. Similar immunoregulatory networks have been proposed in EAE and are discussed here in the context of CNS trauma and neurodegenerative disease.