Why Long COVID throws the body out of balance

Many people still feel exhausted months after a coronavirus infection and struggle with palpitations, dizziness or fluctuations in blood pressure. These symptoms are now summarised under Long COVID or post-COVID syndrome (PCS).

A new study by Prof Dr Boris Schmitz, Prof Dr Frank C. Mooren and their team from the Chair of Rehabilitation Sciences at Witten/Herdecke University (UW/H) has now shed more light on one of the central questions: Why do some people stay ill for so long? The results of the study show that certain autoantibodies could play an important role in this.

What are autoantibodies - and why are they relevant?

Antibodies are proteins of the immune system that recognise and fight pathogens. Autoantibodies are antibodies that are mistakenly directed against cellular structures of the body. They occur in various diseases - such as rheumatism or thyroid disorders.

In the new study, the UW/H researchers investigated autoantibodies that are directed against G protein-coupled receptors (GPCR). These receptors control important processes in the body: heart rate, blood pressure, respiration, stress reactions. If autoantibodies intervene here, this can have serious consequences.

One autoantibody stands out in particular

The researchers examined 105 people with long COVID. One particular autoantibody stood out in some of the patients: CXCR3ab. Its presence is associated with several symptoms that many Long COVID sufferers are familiar with:

• Reduced parasympathetic activity: the parasympathetic part of the nervous system ensures rest and recovery. High CXCR3ab levels weaken this "braking function" - especially at night.
• Higher 24-hour blood pressure and greater increases in blood pressure under stress.
• Lower oxygen saturation during physical activity.

"We see evidence that this autoantibody unbalances the nervous system," says Prof Dr Boris Schmitz. "This could explain why long-COVID patients often feel as if their body is permanently stuck in stress mode."

Several autoantibodies, many effects

In addition to CXCR3ab, other autoantibodies were found that also influence the control of the heart and circulation.

At the same time, there was no evidence in the study that Long COVID leads to a classic, comprehensive autoimmune disease with increased inflammatory factors. Instead, the autoantibodies formed appear to specifically influence certain receptors and regulatory mechanisms - without derailing the entire immune system.

An important building block in understanding long COVID

In some Long COVID sufferers, misdirected immune reactions therefore contribute to the autonomic nervous system no longer balancing the heart, circulation and blood vessels correctly. This explains many typical symptoms - without the heart itself being damaged.

"Our findings don't explain everything," says Prof Dr Frank C. Mooren. "But they show a clear biological mechanism that makes long COVID more understandable - and may also open up new approaches for future therapies."

Further information: The study was published in the Journal of Allergy and Clinical Immunology - one of the leading journals in the field of immunology.