Health

COVID-19: Anxiety and stress make the immune system vulnerable | Knowledge and environment | DW

It should come as no surprise to anyone that stress is bad for your health. Mental stress and anxiety can have a direct impact on the human immune system, making us more susceptible to disease. It was not clear exactly how this mechanism works.

Until now.

Wolfram Poller, cardiologist and researcher at the Charité in Berlin and at the Icahn School of Medicine at Mount Sinai in New York, together with a team of researchers, was able to demonstrate in a study on mice that certain regions of the brain are responsible for determining the movement of leukocytes in the body is responsible – and thus how susceptible an organism is to viral infections.

Stress actually makes you sick

“What was most exciting for me was seeing the huge impact that a few hundred neurons in the hypothalamus have on millions of leukocytes throughout the body,” Poller says.

Neurons set in motion a complex set of interactions between three endocrine glands, the hypothalamus, pituitary and adrenal cortex. This so-called stress axis controls many stress reactions in the body.

Poller and his colleagues conducted their study in mice, some of which they repeatedly exposed to stressful situations. The animals were locked in a cylinder, moved to a new cage or exposed to the smell of urine from natural predators.

The researchers observed that some leukocytes in the mice withdrew into the bone marrow and, put simply, no longer did their job. This made stressed animals particularly susceptible to SARS-CoV-2 or influenza infection. The animals not only became seriously ill more quickly, they also died more often.

leukocytes, granulocytes and lymphocytes

Leukocytes are also called white blood cells. They form in the bone marrow and perform various functions in the immune system.

Leukocytes include granulocytes, which are part of the non-specific immune system. In the event of an injury, they can fight off invading bacteria and parasites without being specifically responsible for a pathogen.

Lymphocytes, on the other hand, which also belong to white blood cells, are specialists. They include T and B lymphocytes, which target specific antigens, i.e. proteins of a pathogen, and render them harmless. In the case of SARS-CoV-2, these include the now known spike proteins.

Stress pushes lymphocytes into the bone marrow

Poller and his team observed that these lymphocytes withdraw in stressful situations. Normally, lymphocytes are found in the so-called lymphatic organs: spleen, thymus or lymph nodes. In stressed mice, they withdrew into the bone marrow.

Poller cannot say for sure whether this mechanism can be transferred to humans in the same way. But the stress axis that became active in mice also exists in humans. It is therefore obvious to the researcher that fear and stress can also make the human immune system more susceptible to viral diseases.

The concentration of granulocytes increases

As unfavorable as lymphocyte withdrawal is in stressful situations in the case of viral infections, something else happens in the body, at least in the bodies of the mice that Poller and his colleagues studied: they observed an increase in granulocytes shortly after the mice had been stressed .

It makes perfect sense that this first, non-specific defense of the immune system is activated in a situation of great fear, which can result in an escape or a fight. “The body is then prepared for injury,” says Poller.

Does Stress Reduce Vaccination Success?

The researcher is therefore thinking of another study, this time with the man. However, they should not be intentionally frightened, but – on the contrary – achieve a particularly balanced state with measures to reduce stress.

Then he wants to vaccinate her against COVID-19. Poller assumes it comes from data collected from the mouse study: “If a weaker specific immune response against a SARS-CoV-2 infection develops under stressful conditions, there may also be a weaker immune response when vaccinated against the virus, when you’re stressed. And in the case of vaccination, you want to get that strong immune response right now. ”

The formation of specific antibodies and T lymphocytes would be inhibited due to stress and the risk of reinfection and disease would be greater. The data directly supporting this hypothesis does not yet exist, Poller points out. However, it can be said with relative certainty: less stress doesn’t hurt.

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