Years ago, in the medical school I learned about various parts/systems in our body. But nobody spent much time in putting everything together. Nowadays I think the situation is still the same and most doctors end up looking at our bodies as a piece here and there. Of course having so many specialized doctors does not help the integration cause.
Over the last year I spent some time reading about the interactions between the immune system and the nervous systems. Depending where we draw the line I would argue that the immune system and the nervous system are basically one thing. The immune system can be seen as part of the sensory system with a role to inform the brain about potential bacteria/viruses present around the body. Nervous system also modulates the immune system. An interesting presentation by Kevin Tracey (TEDMED talk) describes how the vagus nerve changes the immune response. Another lecture by him goes even in more details: the academy of medical sciences talk. Currently there are efforts to use vagus nerve stimulation to treat autoimmune diseases like Crohn’s disease and rheumatoid arthritis (one article here).
The central nervous system (brain and spinal cord) has a significant amount of immune cells in the form of microglia. It is estimated that microglia are 10-15% of all glial cells in the brain. Microglia are tightly integrated with neurons and have a role in the maintenance and regulation of the synapses between neurons. Things can go wrong. There are theories that some forms of depression are caused by inflammation. Charles Raison is one physician researcher who is working on depression and immunity (this interview with Rhonda Patrick is really good). The other day I read an article in the New York Times where cases of schizophrenia seemed to be related to the immune system. In this article one patient developed what appeared to be schizophrenia, then developed leukemia and had stem cell transplant. His schizophrenia resolved after the stem cell transplant. Another patient had leukemia and got stem cell transplant from his brother who had schizophrenia. Strangely enough this second patient developed schizophrenia himself.
The connection between the immune system and the nervous system has been used for thousands of years in yoga and practices of breathing exercises. One recent version is the Wim Hof method which is a combination of cold exposure, meditation and breathing exercises. For a perspective about Wim Hof, the man, this is a good documentary by Vice. Luckily some researchers got involved and they showed that the practitioners of Wim Hof method had a different response when they were injected with Escherichia coli endotoxin. You can read the article published in PNAS for free: here. Anecdotal evidence from the followers of Wim Hof method suggests an improvement of the autoimmune diseases. There is a book by Scott Carney that discusses more on this topic: link here.
This post is just a little introduction on the this topic. My interest is in chronic pain and I think inflammation and pain create a vicious cycle that maintains both of them. We have to start looking at the bigger picture when we treat complex diseases like chronic pain.