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

It should come as no surprise 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 worked.

Until now.

Wolfram Poller, a cardiologist and researcher from Charité in Berlin and at the Icahn School of Medicine in Mount Sinai, New York, and a team of researchers have shown in a mouse study that certain areas of the brain are responsible for the crucial leukocyte movement in the body – and therefore how the organism is susceptible to viral infections.

You are actually sick of stress

“The most exciting thing for me was seeing the massive impact of several hundred neurons in the hypothalamus on millions of leukocytes throughout the body,” says Poller.

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

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

The researchers observed that certain leukocytes in the mice had receded into the bone marrow and, to put it simply, were no longer doing their job. This caused stressed animals to be particularly susceptible to SARS-CoV-2 infection or influenza. Animals not only became seriously ill more quickly, but also died more often.

leukocytes, granulocytes and lymphocytes

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

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

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

Stress drives lymphocytes into the bone marrow

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

Poller cannot say with certainty whether this mechanism can be transmitted to humans in the same way. But the stress axis that has been activated in mice also exists in humans. Thus, it is clear 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 it is to remove lymphocytes in stressful situations in the case of viral infections, something else happens in the body – at least in the bodies of mice that Poller and colleagues studied: They observed an increase in granulocytes shortly after the mice were stressed.

It makes perfect sense that this first, non-specific defense of the immune system is activated in a situation of great fear, which may be followed by flight or fighting. “The body is ready for injury,” says Poller.

Does stress reduce vaccination success?

The scientist is therefore thinking about another study, this time with humans. However, they should not be deliberately frightened, but – on the contrary – to achieve a particularly balanced situation through measures to reduce stress.

Then he wants to vaccinate her against COVID-19. Poller assumes that he is based on data collected from a study in mice: “If a weaker specific immune response against SARS-CoV-2 infection develops under stressful conditions, a weaker immune response may also occur when vaccinated against the virus. when you are stressed. And in the case of vaccination, you want to achieve that strong immune response right now. ”

The production of specific antibodies and T cells would be inhibited by stress and the risk of reinfection and disease would be greater. Data that directly support this hypothesis do not yet exist, Poller emphasizes. However, it can be said with relative certainty: Less stress does not hurt.

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