Why some Covid 19 patients become seriously ill and end up in intensive care is still unclear. In an interview, an expert explains what an essential role the immune system could play.
The immunologist Professor Dr. Andreas Radbruch already has the t-online podcast “Soundtrack Knowledge” talked about the effects of the coronavirus on the body. In an interview, he explains why the immune system can make Covid 19 disease worse and what he thinks of the current research on the bradykinin hypothesis.
t-online: Professor Radbruch, new research shows that hormones could be responsible for many serious Covid-19 cases. The so-called bradykinin hypothesis states that the coronavirus disrupts the body’s own functions such as regulating blood pressure and leads to an overreaction of the immune system. As an immunologist, how do you rate this theory?
Prof. Radbruch: I am somewhat surprised at the response to this study in the public media. In itself, this is relatively trivial. Because the immune reaction in Covid-19 patients can lead to inflammation and this is accompanied by vasodilating hormones. In this case a so-called peptide hormone with the beautiful name “Bradykinin”. This is not very different from histamine. A Dutch research group put forward this hypothesis in April and brought bradykinin into play. The new US study simply evaluated the research of others and wrote it down on paper.
(Source: Gero Breloer)
Prof. Dr. Andreas Radbruch is Scientific Director of the German Rheumatism Research Center and President of the European Federation of Immunological Societies.
According to the study authors, the body keeps making bradykinin, which cannot be broken down. A “bradykinin storm” is said to be responsible for many deaths in Covid 19 patients. Do you find that plausible?
I don’t think you can call that a storm. I see this more as a reflection of the ongoing illness that can drag on for weeks and months. Unfortunately, some of the patients are in the intensive care unit for a very long time. For me this shows that there is a serious inflammation going on there. Whether the coronavirus constantly causes cells to produce bradykinin is complete speculation.
It is also very difficult to detect the bradykinin. That did not happen in the study. If they had at least measured that the bradykinin itself is extremely highly concentrated on site, then you would have proof.
A “cytokine storm” was also mentioned in previous studies …
This refers to inflammatory cytokines that are suddenly released in large quantities. There was literature that claimed that Covid-19 patients suffered sepsis as a result, i.e. blood poisoning. The effect is comparable to an anaphylactic shock: If you are allergic, it can happen that a bee sting is enough to kill you.
But I think that it is not appropriate to call it a storm here either. Because the patients are not in a stormy, but a chronic inflammatory situation. A storm would pass again. Then one comes Sepsis it is also very dangerous. At the beginning it is extremely intense and then you recover from it – or not. Controlling sepsis is still a huge medical problem today.
Is it true that there are gender differences and that men are more prone to overreacting the immune system?
Yes, it seems that the reactions in women are milder. Men react more violently. The reasons for this are still unclear.
This is also the case with autoimmune diseases, some of which are mainly men, others more women. With women, the whole thing is more balanced. To this day it is not known exactly why, for example, predominantly women Lupus and not at least as many men.
You yourself examined the immune response of Covid 19 patients in a research team in the intensive care unit at the Charité in Berlin. What are your findings?
In our manuscript we describe that that Coronavirus triggers a chronic immune response. In the seriously ill patients we look at in the intensive care unit at the Charité, the virus disappears after a certain time – but the immune reaction and thus the inflammation continue. The body tries to slow down the immune response, but it fails. Why this is the case with some Covid 19 patients and not with others is still a great mystery. It can be assumed that it has to do with how the infected person’s immune system deals with the virus. Whether it will find a way to clear up the coronavirus efficiently and quickly or not.
Charité – Universitätsmedizin Berlin: Seriously ill Covid 19 patients are treated here. (Source: Panama7 / Getty Images)
We also suspect that an autoimmune reaction is triggered. There are many diseases, such as chronic intestinal inflammation, where the immune system reacts against its own components, but it shouldn’t react against them. The cytokine we looked at is called TGF-β. Patients develop more and more of it over time; the cells in the lungs, for example, are full of it. The cytokine was supposed to suppress the immune response, but it doesn’t. Patients are then treated with medication to manage symptoms. But the cytokine also has the unfriendly side that it can lead to scarring in the lung tissue. This is a side effect that has been used in severe cases of Covid-19 has been described.
This can lead to long-term damage …
Exactly, the mucous membranes can scar. The tissue is then sometimes no longer functional.
Does it play a role in the severity of the disease, how strong the immune system is before the infection?
Patients who suffer from a suppressed immune system, for example rheumatism, are not recommended to reverse immunosuppression. You should keep taking your medication. So it seems to be different whether you inhibit chronic inflammation or have an acute immune reaction against a pathogen. So far there is no evidence that these patients with suppressed immune systems react worse to the virus.
Rather, it seems to be the case that most people infected with corona already have some kind of pre-conditioning because the body has already gone through something similar with related pathogens. The immune system then has memory cells. So if someone has been infected with other cold viruses, it can get on very quickly and efficiently SARS-CoV-2 responds. On the other hand, the patients who don’t do this are in a bad way. That seems to be much more important as to whether someone has to go to intensive care or not. The dose of the pathogen, its vitality and its ability to penetrate into the depths of the lungs also determine the course.
Thank you for the interview, Prof. Radbruch!
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