Microglia and the Cerebral Defence System

Summary

Mechanisms of microglial activation do not only concern neuroscientists with specialized interest in glial physiology. Microglial cells are gaining attraction as these cells represent the primary sensors and response elements in virtually any neuropathology. As macrophage-like cells they represent a CNS-intrinsic element of innate defence mechanisms. The inducible synthesis of chemoattractive and immunoregulatory factors and the ability to present antigen help the recruitment of leukocytes and the engagement of adaptive immune responses. Even though the primary functions of microglia serve the defence and protection of the nervous tissue the beneficial contributions of these cells are only now being increasingly acknowledged. Indeed, microglial cells appear to safeguard and support neuronal functions, always being ready to transform into alerted states upon challenges by foreign material or disturbances in the CNS homeostasis. Deregulated or dysfunctional microglia can, on the other hand, be critical or at least instrumental in a harmful way. Excessive and chronic reaction of microglia can then fuel destructive cascades upon trauma or during inflammatory and neurodegenerative processes. As the signals and mechanisms of microglial activation become illuminated hope builds up on strategies for selective interference with its undesired outcomes in favour of the overall beneficial potential.