- The immune system was thought to function independently from the brain, with the blood-brain barrier specifically segregating the immune cells that work in the brain.
- More recent evidences point to the impact that the blood's immune system could have on the brain through certain epigenetic activity.
- Activity of certain genes that perform important immune regulatory functions in the blood also link brain structure (thickness of cortex) and memory.
The immune system in the body performs essential functions such as protecting the body from invading pathogens and growing cancer cells. The blood-brain barrier protects the brain from the immune cells in the bloodstream. The barrier also protects the brain from pathogens and toxins circulating in the blood.
The immune cells of the body are divided into:
- those that function in the blood
- those that work specifically in the brain
Up until now, the brain was thought to be unaffected by the peripheral immune system.
‘The epigenetic link between the cells in the immune system and its correlation with brain structure might be used to differentiate between physiological and pathological age-related cognitive decline and cortical thinning.’
More recently, there have been more evidences pointing to the relationship between the blood's immune system and the brain.
Two independent studies have been carried out by the scientists from the University of Basel's Transfaculty Research Platform Molecular and Cognitive Neurosciences (MCN) to demonstrate the strong link between the immune system and brain.
Study 1- Epigenetic Profile
The first study included searching for epigenetic profiles, i.e. regulatory patterns, in the blood of 533 young, healthy people.
An epigenetic profile that is strongly correlated with the thickness of the cerebral cortex was identified. Cerebral cortex is a region of the brain that is important for memory functions.
In an independent examination that involved 596 people, it was confirmed that those genes are specifically responsible for the regulation of important immune functions in the blood. This explains the link between the epigenetic profile and the properties of the brain.
Study 2- Identifying a Gene variant
The genomes of healthy participants who had particularly well or particularly poorly memories of negative images, were investigated.
A specific TROVE2 gene variant was linked to the participants' ability to remember many negative images, while their general memory remained unaffected.
Increased activity in specific regions of the brain linked to memory of emotional experiences was also caused by the gene variant.
In people who have experienced traumatic events, the gene is also linked to the strength of traumatic memories.
"Although the precise mechanisms behind the links we discovered still need to be clarified, we hope that this will ultimately lead to new treatment possibilities," says Professor Andreas Papassotiropoulos, Co-Director of the University of Basel's MCN research platform.
The researchers hope to better understand human brain functions and to develop new treatments for psychiatric disorders.
The findings are published in Nature Communications
- Author name. title. A peripheral epigenetic signature of immune system genes is linked to neocortical thickness and memory. Nature Communications; (2017)