Impact of the Immune System on the Brain and Mental Health

Most are aware that neurons send neurotransmitter signals to each other in circuits within the brain. My new book, The Secret Language of Cells, shows that similar conversations occur among all the cells in the body and these wide ranging conversations determine all physiological functions. While there are numerous examples of this cellular communication in the book — such as capillary cells sending directional signals for white blood cells to find an infection and capillaries instructing stem cells how to produce particular cells for the brain, this article will focus on a few ways that cellular conversations among immune cells and brain cells affect mental health. 

Two-way cellular conversations between traveling immune cells and stationary brain cells use signals that are sent as molecules, or molecules inside sacs, that are secreted into tissues, blood vessels, and cerebrospinal fluid. The signals can profoundly affect general cognition and memory, and are highly related to depression and pain, as well as responses to stress. 

For many of the major influences on the brain, signals are sent by T cells that travel in the cerebrospinal fluid (CSF). These T cell signals are relayed to specific regions of the brain by special lining cells