Basic mechanisms of brain inflammation.

The mechanisms, how the immune system surveys the nervous tissue and how brain inflammation is regulated are essential questions for therapy of neuroimmunological diseases. The nervous system is continuously patrolled by hematogenous cells, which may pass the blood brain barrier in an activated state. When these cells find their respective target antigen in the CNS compartment, an inflammatory reaction is started through the secretion of proinflammatory cytokines. This leads to the upregulation of endothelial adhesion molecules and the local production of chemokines, which in concert facilitate the entry of inflammatory effector cells into the lesions. T-lymphocytes are effectively removed from inflammatory brain lesions by local apoptosis. In addition some lymphatic drainage of the nervous system allows the removal of effector cells from the lesions and their migration into regional lymph nodes. In summary these data suggest that the immune surveillance of the central nervous system is much more tightly controlled compared to that in other organs.