The immune cells were stimulated with small, artificially produced fragments of the so-called spike protein from Sars-CoV-2. The research group then checked whether the T-helper cells had been activated by the protein fragments.
In 15 of the 18 Covid-19 sufferers, the T helper cells reacted to the fragments of the virus surface. This was not to be expected, since the patient’s immune system was fighting the new virus – it had to react to it in a test tube. Why not everyone? T cells may not be activated outside the body in an acute or particularly severe stage of a disease.
To the team’s surprise, reactive T helper cells were also found in the blood of healthy people. 24 of the 68 tested (35 percent) had memory cells that recognized Sars-CoV-2 fragments.
The scientists noticed that the immune cells of Covid 19 sufferers and healthy people reacted to different parts of the virus envelope. While the patient’s T helper cells recognized the entire length of the spike protein, the healthy T helper cells were activated primarily by sections of the spike protein that resemble more harmless common cold coronaviruses.
“This indicates that the healthy T-helper cells react to Sars-CoV-2 because they have had to deal with local cold coronaviruses in the past,” said Giesecke-Thiel, one of the three leading authors of the study .
“Because one of the properties of the T helper cells is that they can be activated not only by an exactly ‘suitable’ pathogen, but also by ‘sufficiently similar’ intruders.” In fact, the research group was able to demonstrate that the T helper cells of the healthy volunteers who responded to Sars-CoV-2 were also activated by various common cold coronaviruses – and by definition “cross-reacted”.
Follow-up study: Scientists are looking for recovered Covid and cold patients
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