Seeing sick faces revs up our immune system, new data show

Just seeing someone who looks sick may trigger our brains and bodies to go into infection-fighting mode.

This finding comes from people who viewed faces in virtual reality. If the faces were of individuals who seemed to be sick, the viewers’ own brains became active in areas that detect threats. Certain immune cells in the viewers’ blood also became active.

A research team in Europe shared the new findings in the September issue of Nature Neuroscience.

This is “really remarkable,” says Michael Irwin, who did not take part in the new work. It’s the first study, he says, to show that just seeing someone who looks sick can rev up our immunity. His own work at the University of California, Los Angeles, has focused on how the brain interacts with our immune system.

Explainer: The body’s immune system

For the new study, 248 recruits watched faces approach them in virtual reality. At the same time, researchers monitored brain activity and the blood of these viewers.

Some avatars showed signs of sickness, such as coughing or rashes. Others appeared fearful or neutral. Some study participants saw sick-looking avatars entering their personal space. They reacted faster to their face being touched, researchers found. That faster reaction suggests these participants were on the alert.

Brain regions that monitor personal space reacted differently to sick faces than to other ones. A brain circuit that detects important events in the environment also turned on.

“These two systems were activated differently by a sick avatar,” says Andrea Serino. They were different even from a “fearful” avatar. That suggests the concern was about infection, he says, not threats in general. Serino is a neuroscientist at the University of Lausanne in Switzerland. He coauthored the new study.

Blood responds to viewing ‘sickness’

Certain immune cells in the blood also grew more active in people who saw sick faces. These innate lymphoid cells are one of the immune system’s first responses to a threat. They sound an alarm to other immune cells.

Camilla Jandus is an immunologist at the University of Geneva, in Switzerland. She says she wouldn’t have expected that activation unless or until a pathogen got into the body.

Serino and Jandus were part of a team that compared changes in these people to how the human body reacts to a flu vaccine. That vaccine turns on lymphoid cells similarly to what occurred in people who saw sick avatars, says Jandus. This shows that their bodies responded in much the way they do to being infected with germs.

This discovery might one day be used to boost how well vaccines work. Or it could help certain drugs work better by upping the immune system’s response, Serino says.

First, researchers need to better understand what’s going on. The new study measured only two types of immune cells. And they saw no change in the second type, called natural killer cells.

The immune system is very complex. Much of what it does remains unknown. This study’s analysis of what happened to the immune response is fairly simple, says Filip Swirski. “A lot more should be done to look at this more thoroughly,” he says. An immunologist in New York City, Swirski works at the Icahn School of Medicine at Mount Sinai.

The European group is already working on this. They want to know how long the effects last after seeing a sick face. They also have begun monitoring more cells and molecules.

The current study only focused on young adults. Whether the same thing happens in older people hasn’t been tested. Age, sex and ethnic background may all affect how the body responds, Irwin points out. “All those factors need to be taken into account.”