The brain is the most complex organ in the human body, containing over one hundred billion nerve cells. In contrast to other organs, the brain has a very limit capacity to regenerate. Both microbial infections as well as the host?s own immune response against these microorganisms can irreversibly damage the brain. As a consequence, inadequate and ?hyperactive? immune responses are the root of many diseases including HIV-associated dementia, congenital viral encephalopathy, and multiple sclerosis? a debilitating auto-immune disease of the CNS
