Activated through permanent stress, immune cells in the brain can cause changes to the brain, resulting in mental disorders, a research team headed by professor Georg Juckel, Medical Director of the Ruhr-Universität Bochum (RUB) LWL university clinic, has found. The research was based on psychoneuroimmunology, the study of the interaction between psychological processes and the nervous and immune systems of the human body. The team focused mainly on microglia, a type of glial cell that acts as the main immune defense in the central nervous system and comprise 10–15% of all cells found within the brain. Under normal circumstances, microglia repair synapses between nerves cells in the brain and stimulate their growth. Repeatedly activated, however, microglia may damage nerve cells and trigger inflammation processes — a risk factor for mental diseases such as schizophrenia, the researchers found.
Interactions between the brain and immune system
“Originally, the brain and the immune system were considered two separate systems,” explains Juckel in RUB’s RUBIN publication. “It was assumed that the brain operates independently from the immune system and has hardly anything to do with it. This, however, is not true. “Direct neural connections from the brain to organs of the immune system, such as the spleen, do exist. And vice versa, immune cells migrate to the brain, and local immune cells carry out various tasks there, including disposing of damaged synapses. Notably, treatment with an immune system mediator such as Interferon alpha, used in hepatitis C treatment, for example, leads to depressions in 20 to 30 per cent of the patients.
Picture: Microglia cells from rat cortex before (left) and after (right) traumatic brain injury