Here’s a surprise: there are lymphatic vessels going into the brain. That’s reported in this paper in Nature. (Here’s a pretty breathless press release from the University of Virginia, where the work was done). I’m no immunologist, but the work (done mostly in mice, and extended to human samples) looks pretty solid to me.
We were just having a discussion around this site about the immune system and the brain, and this discovery is going to set off a lot of research on that topic. Here’s how the authors finish off the paper:
The presence of a functional and classical lymphatic system in the central nervous system suggests that current dogmas regarding brain tolerance and the immune privilege of the brain should be revisited. Malfunction of the meningeal lymphatic vessels could be a root cause of a variety of neurological disorders in which altered immunity is a fundamental player such as multiple sclerosis, Alzheimer’s disease, and some forms of primary lymphoedema that are associated with neurological disorders.
That seems like a bit of a leap, but not a crazy one. The state of this part of the lymphatic system in various diseases is now officially a big topic, I’d say. The authors already seem to have both demonstrated its existence and some real differences between it and the more well-known lymphatic vessels, and there will surely be more to come. Who knew?