The brain may serve as a watchtower for the immune system. It spots possible infection threats and sounds the internal alarm. As a result, the immune system may react before a virus ever enters the body.
A new study explored how the brain senses and prepares for infection. The findings show how this early response may prime immune defenses in advance.
Researchers used virtual reality to show sick avatars approaching participants. These avatars moved into participants’ peripersonal space—the area immediately near the body. The brain responded to this possible threat before any real contact happened.
How Did Researchers Show the Brain’s Pre-infection Response?
Multisensory and motor brain regions detected the avatars’ signs of infection. These areas activated the salience network, which spots important sensory cues. The team used psychophysics, EEG, and fMRI to measure this brain activity.
This early brain activity affected the body’s immune system as well. Participants showed changes in both number and activity of innate lymphoid cells. These are fast-acting immune cells that respond during early infection.
The brain’s threat response also changed its connection to the hypothalamus. The hypothalamus controls many body systems, including stress and immune responses. This suggested a link between brain signals and the body’s stress response.
Researchers found this pattern involved the hypothalamic–pituitary–adrenal (HPA) axis. This axis helps control hormones and immune system readiness during stress. Brain chemicals likely mediated the immune signal from the hypothalamus.
A neural network model helped confirm the brain-immune connection. It showed how early brain activity could trigger immune changes. This adds new insight into how the brain prepares the body for danger.
How Did the Study Simulate and Detect Responses to Signs of Infection?
A total of 248 people took part in five experiments. Groups were matched by age and sex, with 132 women total. Average age was 26.8 years, ranging from 18 to 49. No participants had major health issues or somatosensory problems. Everyone had normal vision or used corrective lenses.
Participants were placed in groups for avatar testing or vaccines. Each group was tested in the morning to limit biological variance. VR and blood testing happened during 8:30 a.m. to 12:30 p.m. Each participant only joined one experiment in the study.
VR used Oculus Rift headsets to display 3D avatar faces. Each avatar matched the participant’s gender and facial orientation. Avatars looked either neutral, fearful, or visibly sick.
Participants responded to touch while avatars approached in VR. They pressed a button quickly after each face-touch pairing. Reaction time (RT) was measured based on avatar distance. This helped define how close avatars had to be to trigger faster reactions.
Sixty people gave blood before and after two VR sessions. The second VR session included a break between two exposures. Blood was processed to isolate immune cells and serum for testing. A separate vaccine group gave blood before and after flu shots. Sample sizes and timing were equal across all groups.
Immune response focused on ILCs and NK cells in blood. Samples were labeled with fluorescent antibodies for specific cell markers.
Conclusion
A recent study shows how the brain can trigger immune responses before infection. Just seeing a possible threat is enough to prepare the body.
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Logan Hamilton is a health and wellness freelance writer for hire. He’s passionate about crafting crystal-clear, captivating, and credible content that elevates brands and establishes trust. When not writing, Logan can be found hiking, sticking his nose in bizarre books, or playing drums in a local rock band. Find him at loganjameshamilton.com.
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