There's a lymph system in the brain that was so subtle that it went undiscovered until 2016. Lymph nodes are centralized pathogen collectors in the body's immune response system that allow the body to determine an appropriate immune response. There may be a connection between immune response and cognition, now that these nodes have been discovered in the brain. Not much else is known at this time.
It's particularly interesting given that it followed up on earlier stories related to the waste clearance in the brain. You can read up more at https://en.wikipedia.org/wiki/Glymphatic_system
there is a series of ducts throughout the body that also incorporate with the brain at gross anatomic scale.
this is a newly recognized feature.
it makes sense considering some neurological disorders seem to be associate with immune dis/function
I specifically wonder about autoimmune conditions and allergies in this context.
so are many others, there could be some very new opportunities to understand for pathology, therapy, and disease processes in general, even the whole mind over matter thing, psychosomatic illness, etc.