Immune system: We alert the brain to our defenses

If it happens on the train or on the bus, we can usually dodge: a woman sneezes loudly, a man roars and looks very pale, a child coughs out of full lungs.

However, our escape options are more limited in the full cinema or in the theater when aerosols and infectious droplets are the breath tract of a person who sits near us, as if left from a spray bottle. However, even then we are not completely helpless, as the study of a team from the Swiss universities Geneva and Lausanne in the journal “Nature Neuroscience” could show: For now, it is enough to only discover a source of infection near us to alert the concentrated body defense.

One of the advantages of our basic equipment inherited by evolution is that we are constantly observing our surroundings as in the radar. To do this, we don’t even have to turn our heads or consciously open their eyes and ears. Because this surveillance system works autonomously, i.e. regardless of our consciousness. However, it demands our attention in a flash if, for example, unexpected things are happening and possibly threatens. Then it means to counter the threat or to search for the width. This reaction is mostly scientifically mentioned as a reflex reaction “Fight or Flight”. So what happens when a potential source of infection approaches us?

In order to find out, a total of 248 healthy volunteers (average age of just under 27, about half of women) have now been asked to the laboratory and equipped with VR glasses, which allowed the test subjects to at least virtually put them in such a situation. Of course, it did not correspond exactly to everyday life. But the instrument of a laboratory is not available in the bus or in the cinema. In addition, it would not be ethically justifiable to suspend people for such an attempt to have a real risk of infection. So the threat was virtually generated in the glasses. And that was enough to get exciting insights.

In the case of introductory studies by all subjects, the main thing was to rule out psychological peculiarities – such as a striking anxiety or a special sensitivity to disgust. All trial volunteers should bring the same prerequisites as possible from their physical and mental health so that the actual measurement results were not distorted in the experiments. Then three groups were formed and confronted with different avatars: First, this was a face generated by the computer with a neutral expression. The second avatar wore a large -scale reddish rash with an indicated suffering dates. In a third version, the rash was missing, but the facial features were distorted as in fright.

For all three situations generated in the VR glasses, not only the reactions of the brain were measured, but also the concentration of certain immune cells in the blood of the test subjects. And as soon as the supposedly contagious avatar entered to the “peri -personal space”, they actually stirred. Or simply said: he had to put the test subject on the pelle.

The room right next to our body is something of a private restricted zone that is even monitored in the brain by its own neural system. As a concept of mental concept, this zone was developed with quite variable and situation -dependent limits in the 1960s. Accordingly, this navigation begins where it becomes uncomfortable for us if strangers should continue to come to us. In fact, it can actually be measured in overcrowded lanes or buses how the stress level of passengers moves up if a distance perceived as a pleasant distance can no longer be observed.

That is why it was this “peri -personnel space” that particularly interested the researchers: How would the virtually established source of infection work if it got so close to the subjects? The observed brain activities in this situation corresponded to expectations. The alarm system ignited and triggered the “Fight or Flight” reflex. In addition, areas in the brain became active, of which previous examinations were already known that they act on the immune system.

Didn’t the border crossing by the avatar be able to be demonstrated biochemically in the body of the test subjects? In fact, in the rehearsals of the subjects left to the vein, certain types of white blood cells (“innate lymphoid cells” and “natural killer cells”) were found that belong to the innate first line of defense in our body and can be mobilized if necessary. And that was exactly what happened when a sick face approached. On the other hand, the immune cells were not activated in the event of a neutral facial expression of the other person in the VR glasses and not even if this face was anxiously distorted and therefore no contagion, but indicated any closer danger nearby.

The fact that the immune system had really had a risk of infection was shown during the control examination with a comparison group that did not even have to put on the VR glasses. Instead, she was only vaccinated against the seasonal flu – with a real pik, not virtual. Because even such a vaccination activates the immune system and pretends a real infection without being able to actually trigger it. The concentration of the corresponding immune cells and thus the activity of the first line of defense corresponded to the values that had also been measured under the VR glasses in the supposed threat.

The subjects even knew that they were in an experiment and that they did not meet a real person and therefore no real danger in the field of view of the VR glasses. For the autonomous brain, however, this made no difference, and the defense was high as a precaution – an encouraging result. Because it means that we are constantly on the hat. Of course, this first congenital defense line does not replace any vaccinations and no rules of conduct, as we know it from pandemic to avoid infections completely as possible. But it is reassuring to know that we are apparently never completely defenseless.