Friday 30 June 2017

Link between the immune system and brain function

Insights from clinical PNI are increasingly finding their way to mainstream medicine. A recent study published in Nature Communications reveals, for example, that there is a link between immune functions in the blood and brain function.


Scientists at the University of Basel in Switzerland have proven in two independent studies that there is a link between the brain and immune cells in the blood. The results have been published in the scientific journals Nature Communications and Nature Human Behaviour.


Link between the brain and immune system

The immune system fulfils an essential role in the body, for example, in defending the body against ‘unwanted intruders’. However, the blood-brain barrier ensures that these immune cells are unable to enter the brain, including as pathogens and toxins.


In the brain itself, only brain-specific immune cells appear to be active. Until recently, the most widely held view was therefore that the brain function is largely independent of the peripheral immune system. The two studies at the University of Basel now demonstrate that this isn’t the case.


Epigenetics is the missing link

During the first study, the blood counts of 533 healthy young people were examined. This revealed an epigenetic profile which correlates closely with cerebral cortex thickness, in this particular part of the cortex that is important for memory.


This result was independently confirmed in another group, comprising 596 volunteers. The conclusion is that there is a correlation between the genetic basis of the immune system in the blood, the epigenetic profile and the structure of the brain. In this case, the epigenetic profile can be seen as the missing link.


Traumatic memories

During the second study, the scientists looked at the genome of healthy volunteers who were either very good or conversely very bad at remembering negative images. It was found that a variant of the TROVE2 gene is responsible for people remembering many negative images, whilst the remainder of the memory was unaffected. The variant of the TROVE2 gene was also responsible for increased activity in specific areas of the brain that are important for remembering emotional experiences.


The researchers revealed that the gene is linked to the strength of traumatic memories in people who have suffered traumas. The gene is usually only investigated in the context of immunological disorders.


Treat the immune system and brain together

According to the scientists, the results of the two studies show that brain structure and memory are linked to the activity of genes that also have an important regulatory function within the immune functions in the bloodstream.


"Although the exact mechanism behind this link must still be clarified, we hope that these insights will translate into treatment options”, say the researchers.


The study also possibly explains the fact that, for example, a vitamin D deficiency contributes to both immune system-related problems (including multiple sclerosis) and psychological problems (including autism, depression).



Virginie Freytag et al., A peripheral epigenetic signature of immune system genes is linked to neocortical thickness and memory, Nature Communications 8 (2017), 15193

Angela Heck et al., Exome sequencing of healthy phenotypic extremes links TROVE2 to emotional memory and PTSD, Nature Human Behaviour 1 (2017), 0081