Brain and Body Collaborate to Proactively Prepare Immune Defenses Against Infections

The brain and body have a remarkable ability to work together to prepare immune defenses against potential infections, even before any physical contact with pathogens occurs—this is the key finding of a new study published in Nature Neuroscience.

Traditionally, threats from predators trigger the well-known "fight-or-flight" response, but pathogens like bacteria and viruses pose a more subtle, silent risk. Contact with pathogens activates the body’s immune response, including rapid reactions from innate immune cells and slower adaptive immune responses. However, how the brain and immune system collaborate before an infection takes hold has long been unclear.

To explore this, researchers led by Camilla Jandus and Andrea Serino from the University of Lausanne (Switzerland), along with their colleagues, designed a VR experiment involving 248 healthy young adults. Participants were exposed to virtual human faces: some showed visible signs of infection (e.g., rashes, coughing), while others displayed neutral or fearful expressions. When virtual figures with apparent illness entered the participants’ "near-body space" (the close proximity around the body), the participants exhibited stronger reactions to touch, indicating that the brain’s near-body space system was in a state of heightened alertness.

Using electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) to measure brain activity, the team found that when infectious-looking figures approached, there were changes in brain regions responsible for integrating sensory information and spatial awareness—changes not observed when participants faced neutral or fearful faces. Additionally, blood samples from participants showed elevated activity markers in innate lymphocytes (a key component of the immune system) after exposure to the infected virtual images. This response was comparable to reactions triggered by real infections, such as those induced by flu vaccines.

The study authors conclude that the brain can coordinate early physiological responses when confronted with potential infections, effectively priming the immune system in advance. This proactive collaboration between the brain and body represents a sophisticated mechanism to defend against pathogens, offering new insights into how our bodies prepare for threats before they even materialize.