The complement system in central nervous system diseases.

The activation of complement system is an important factor participating in inflammatory, neurodegenerative, and cerebrovascular diseases. Astrocytes and neurons are able to synthesize complement components. Myelin and oligodendrocyte (OLG) activate the classical pathway of complement in vitro in the absence of antibodies. Sublytic C5b-9 in the absence of cell death induces proto-oncogenes, activates cell cycle, and enhances cell survival in OLG. In addition, C5b-9 reverses the differentiation phenotype in OLG and enhances cell survival. beta amyloid protein is an activator of the complement system and neurons are susceptible to bystander complement mediated damage. These findings indicate that complement activation and membrane assembly of C5b-9 play an important role in pathogenesis of central nervous system (CNS) disorders.