One of the things you will find out about me if you associate with me long enough, is my fascination with the immune system. The immune system is the element of the body that makes legitimate the adage "what doesn't kill you just makes you stronger".
Since I was in graduate school, I have followed the work of those in the field of Neuroimmunomodulation. A really big word that suggests that the immune system and our brain are intimately involved in each others workings. For those of you not in this line of work, that may seem obvious; however, once you are trained as a biomedical scientist you tend to think of the body as several systems working independant of each other. It makes it easier to study them. So those who study the connections between the brain and the immune system have often been relegated to the controversial or fringe sections of the party.
I tend to think of the immune system as a sensory organ for the brain. The brain doesn't get out much, it's pretty difficult to get past the skull and getting into the brain through the blood is highly regulated by the blood-brain-barrier. So if there really is a mind-body connection like so many of us granola types believe, the brain's gotta be getting it's information from somewhere. One place to look is for ways that the central nervous system and the immune system could communicate.
A recent Harvard study explains how a molecule that until now has been relegated to the immune system, plays an important role in the brains ability to make new connections. Something important only if you want to remember things. Not bad for a molecule thought only to train immune cells who to kill. This study is important because any molecule involved in regenerating neural pathways - say after an injury - is a hot topic (think Christopher Reeves). Of course I (and a few others) would think "what is a respectable immune protein doing in that neck of the woods?"
But even cooler than that (yes, I have been called a nerd for this kind of enthusiasm), immunological synapses (pretty picture too) - structures that were thought to reside only in the brain - have been found in the body. Of course it could be that my brain just looks for these connections cause I want to see them.