“Immune System Maintains Brain Health”
by Amanda Keener
The Scientist, November 1, 2016
Immune cells in the brain. Locals or troublemakers?
Assuming you don’t already have one in the works, I would love to write a feature on recent advances in neuroimmunology. The field is booming, so there are a lot of angles to take. I think a good one is to ask what we’re learning about the immune system’s role in normal brain physiology. Historically, immune cells in the brain (besides microglia) have been viewed as a bad sign and a marker of inflammation and disease. But there’s mounting evidence to suggest immune cells are vital for normal brain function and repair after injury or infection.
For example, T cells, which are known to have a role in driving multiple sclerosis (and in mice, EAE), were recently reported to have many positive roles in the central nervous system (CNS). These roles include surveillance for viruses and production of anti-inflammatory and pro-neurogenic cytokines. Mice engineered to lack T cells or that have other T-cell perturbations have memory and learning problems, and Jonathan Kipnis, whose lab studies T-cell biology in the CNS, told me he plans to publish a study this summer showing a role for T cells in brain functions that affect social interaction.
Kipnis’ recent description of lymphatics in the brain also contributes to a view of immune cells as normal inhabitants of the brain and to a revision of the concept of immune privilege in the brain and eye. It also opens up new questions that Kipnis and his colleagues are pursuing about the roles of immune cells and lymphatics in maintaining brain homeostasis and how both change in diseases like multiple sclerosis or Alzheimer’s. I could use examples of recent findings from diseases like these, and in brain injury to lay out the potential implications this new view could have on developing therapies.
I’d want to look at how researchers are distinguishing a helpful immune response in the brain from a harmful one and how they are trying to skew the response toward repair. There’s debate over whether immune signatures associated with neurodegenerative diseases is driving disease and inflammation, or if it’s a sign of attempted repair. This translates to the question of whether treatments for such diseases should focus on suppressing inflammation or promoting immunity.
I would also want to speak with Michal Schwartz, a neuroimmunologist at the Weizmann Institute in Israel. She seems like quite a character and she has advocated for a protective role of the immune system in the CNS for two decades.
Hope this is helpful!