The concept of immune privilege of the central nervous system (CNS) has dominated the study of inflammatory processes in the brain. However, clinically relevant models have highlighted that innate pathways limit pathogen invasion of the CNS and adaptive immunity mediates control of many neural infections. As protective responses can result in bystander damage, there are regulatory mechanisms that balance protective and pathological inflammation, but these mechanisms might also allow microbial persistence. The focus of this review is to consider the host-pathogen interactions that influence neurotropic infections and to highlight advances in our understanding of innate and adaptive mechanisms of resistance as key determinants of the outcome of CNS infection. Advances in these areas have broadened our comprehension of how the immune system functions in the brain and can readily overcome immune privilege.
The CNS utilizes multiple mechanisms to restrict microbial entry but there are also innate and adaptive mechanisms that control pathogens that access this immune privileged site. Klein and Hunter review the pathogen interactions with the blood brain barrier and resident glial populations that govern the outcome of CNS infection, as well as the immune mechanisms that dictate protective and pathological responses in the brain.