Jul 30th 2025|3 min read
THE HUMAN immune system is full of surprises. Though it has long been known that the body’s internal defences spring into action when an infection-causing intruder—such as a bacterium or virus—is detected, a new study published in Nature Neuroscience suggests that the mere sight of an infection may be enough to kick the immune system into gear. The findings could reframe scientists’ understanding of this most complex of biological systems and aid the development of treatments for immune disorders.
To arrive at their conclusion, a team of researchers, led by Andrea Serino, a neuroscientist at Lausanne University Hospital, and Camilla Jandus, an immunologist at the University of Geneva, conducted an experiment using immersive virtual reality (VR) on several groups of volunteers. All the participants, barring those in the control group, were fitted with a VR headset showing a range of onrushing human faces. Some displayed rashes, a visible sign of infection. Volunteers in one group had a device attached to their cheek, through which the scientists could administer vibrations.
As the faces approached, the scientists asked participants to press a button as quickly as possible each time they felt a vibration. The participants’ reaction times were measured, revealing that they were faster to respond when infectious faces loomed. This suggested that their brains were anticipating a potential threat to the body.
This was confirmed with the help of a second group of participants, whose brain activity was monitored while the faces approached. When the infectious avatars approached the participants, regions of the cortex involved in threat detection were more active than when the other avatars approached.
To see if the participants were specifically responding to the threat of infection, rather than just onrushing danger, the authors needed to test if an immune response was triggered in the body as a result. In the third test group, therefore, blood samples were taken from participants immediately after the VR simulation ended.
These showed that in volunteers who had been shown only infectious faces, innate lymphoid cells (ILCs), components of the immune system that secrete proteins to alert other immune cells to the presence of a pathogen, had begun to raise the alarm. The amount of ILC activation seen in the blood samples was similar to that among control participants who were given a flu vaccine and no VR exposure. This led the researchers to conclude that the immune system can be activated simply in response to perceived threats, rather than requiring physical contact with an infectious agent. Mark Schaller, a psychologist at the University of British Columbia who has done similar work in the past, concurs.
The scientists also wanted to understand how the brain communicates the threat of infection to the immune system. The brain-imaging experiments suggested that the messages pass from the cortex to the hypothalamus, which controls bodily functions such as hormone release. The hypothalamus then sends the chemical signals needed to switch on the ILCs.
There are evolutionary reasons why the immune system may have evolved to overreact in this way (panic attacks are another example of such reactions). False alarms and excessive responses are common in living organisms, says Dr Serino, because false positives are generally less risky than false negatives.
The findings could have real-world applications for cases in which the body’s immune defences need a boost. The scientists are particularly keen to study immunotherapy, a form of allergy treatment where sufferers are exposed to a small dose of an allergen in order to train their immune system not to overreact. Dr Serino suspects that exposing a person with a bee-venom allergy to a VR simulation of a bee while at the same administering a dose of the venom could make the treatment more effective at lower doses of the allergen. ■
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