By Timo Kirez
GENEVA (AA) - A German-Austrian research team has identified the cause of so-called post-COVID-19 syndrome, also called Long COVID, in comparative studies of affected individuals.
In a study published Monday in the journal Frontiers in Medicine, the scientists found that the body's defense system appears to be out of balance for a longer period of time after a coronavirus infection.
The experts repeatedly examined the status and subtype distribution of immune cells and other parameters in the laboratory. Concentrations of immune messenger substances (cytokines) were also measured in the blood of the test subjects.
According to the scientists, the studies reveal a certain characteristic. Patients with post-COVID-19 syndrome showed an increased number of CD4-positive and CD8-positive T lymphocytes specifically reacting to SARS-CoV-2 and releasing interferon-gamma and tumor necrosis factor.
Elevated tumor necrosis factor levels in the blood are considered a hallmark of inflammatory processes. At the same time, the cells also had the so-called CD40 ligand surface molecule as a marker. CD40 ensures that antibodies are increasingly released in B cells.
B cells belong to the white blood cells and, together with T cells, make up the adaptive part of the immune system, i.e. the part that can adapt to new pathogens.
So-called dendritic cells, which, for example, take up antigens and present them to the defense system or are important for inflammatory reactions, were also registered in greater numbers in those affected.
The study, the authors said, described changes in immunologic status among individuals who overcame COVID-19 with or without resulting in longer-term health problems.
"This may have potential for future epidemiologic research and targeted therapies," the study stated.
Symptoms that last longer than 12 weeks after a severe infection with the SARS-Cov-2 virus are generally referred to as post-COVID-19 syndrome.
The World Health Organization (WHO) estimates that a total of 10 to 20% of those affected by COVID-19 experienced some form of longer-lasting effects of the infection.