This is quite amazing. The brain has a heretofore undiscovered lymphatic system. That means that the immune cells and the brain are in much closer contact than was ever before imagined. That opens up many more possibilities of brain immune system interaction. Many more possibilities for immune cells to affect the development of psychiatric illnesses. Who knows, lol as I hypothesized in one of my manic phases, mental illness could be an autoimmune disease. Well we’ll just have to wait and see exactly what the implications of this discovery are. At the moment, it just shows us that the brain and the immune system are much more intimately associated than was previously known. 

http://www.neuroscientistnews.com/research-news/missing-link-found-between-brain-immune-system-major-disease-implications