RESTRICTED INFLAMMATORY REACTION IN THE CNS - A KEY IMPEDIMENT TO AXONAL REGENERATION

Axons in the central nervous system (CNS) of adult mammals do not rege nerate after injury. Mammalian CNS differs In this respect from other mammalian tissues, Including the peripheral nervous system (PNS), and from the CNS of lower vertebrates. In most parts of the body, includin g the nervous system, injury triggers an Inflammatory reaction involvi ng macrophages. This reaction Is needed for tissue healing; when it Is delayed or insufficient, healing Is incomplete. The CNS, although nee ding an efficient inflammatory reaction resembling that In the periphe ry for tissue healing, appears to have lost the ability to supply it. We suggest that restricted CNS recruitment and activation of macrophag es are linked to regeneration failure and might reflect the Immune pri vilege that characterizes the mammalian CNS. As macrophages play a cri tical role In tissue restoration, and because their recruitment and ac tivation are among the most upstream of the events leading to tissue h ealing, overcoming the deficiencies In these steps might trigger a sel f-repair process leading to recovery after CNS Injury.