What is immune privilege (not)?
The 'immune privilege' of the central nervous system (CNS) is indispensable for damage limitation during inflammation in a sensitive organ with poor regenerative capacity. It is a longstanding notion which, over time, has acquired several misconceptions and a lack of precision in its definition. In this article, we address these issues and re-define CNS immune privilege in the light of recent data. We show how it is far from absolute, and how it varies with age and brain region. Immune privilege in the CNS is often mis-attributed wholly to the blood-brain barrier. We discuss the pivotal role of the specialization of the afferent arm of adaptive immunity in the brain, which results in a lack of cell-mediated antigen drainage to the cervical lymph nodes although soluble drainage to these nodes is well described. It is now increasingly recognized how immune privilege is maintained actively as a result of the immunoregulatory characteristics of the CNS-resident cells and their microenvironment.
Galea
Ian
I
CNS Inflammation Group, School of Biological Sciences, University of Southampton, SO16 7PX, UK. I.Galea@soton.ac.uk
Bechmann
Ingo
I
Perry
V Hugh
VH
D000818:Animals; D001812:Blood-Brain Barrier / Q000276:immunology*; D001921:Brain / Q000276:immunology; D002490:Central Nervous System / Q000276:immunology*; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology*; D051379:Mice; D051381:Rats