Nikhil Prasad Fact checked by:Thailand Medical News Team Aug 17, 2025 2 hours, 39 minutes ago
Thailand Medical News: The Hidden Role of Natural Killer Cells
A new study from Bulgarian scientists has revealed how a special type of immune cell, known as natural killer (NK) cells, changes its behavior during and after COVID-19 infection. These cells normally act as the body’s frontline defenders, attacking virus-infected cells quickly. However, during SARS-CoV-2 infection, NK cells seem to experience both over-activation and exhaustion, leaving them less effective. This
Thailand Medical News report highlights the findings and explains why they matter.
NK Cells Show Strange Behavior in COVID-19 Patients
The research was carried out by teams from the Medical University of Plovdiv, the Infectious Diseases Clinic at St. George University Hospital, and the Institute of Molecular Biology at the Bulgarian Academy of Sciences.
What the Scientists Did
The researchers studied blood samples from COVID-19 patients during the first few days of infection and again about a month later. They compared these results with samples from healthy individuals. By using detailed immune testing, they looked at different “on” and “off” switches on NK cells, such as proteins that either activate or inhibit their activity. They also tested how well these cells could kill a specially engineered line of target cells.
Key Findings
The scientists discovered that NK cells behaved very differently in patients compared to healthy people. One group of NK cells showed higher levels of both activating and inhibitory signals. This suggested that while the immune system was trying to fight the virus, it was also being suppressed at the same time, weakening the overall defense.
They also found that NK cells were still producing strong amounts of interferon-gamma, a powerful immune signal, even a month after infection. Despite this, when the cells were tested for their ability to kill target cells, they were far weaker—destroying less than half as many targets as NK cells from healthy individuals.
Another NK cell subgroup, which usually carries out strong cell-killing activity, was especially impaired. These cells had low levels of key weapons like granzyme B and perforin. At the same time, one of the most important “activation buttons” on NK cells, called NKp46, was almost absent during infection.
Why This Matters
The findings show that during COVID-19, NK cells may appear highly active but are actually exhausted and less functional. The virus seems to create a confusing state where the immune system is both stimulated and suppressed. This imbalance could explain why some patients have trouble clearing the virus and why others continue to suffer long-term problems.
The researchers suggest that treatments designed to block the inhibitory signals on NK cells could help restore their strength and improve recovery for patients.
Final Thoughts
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This study highlights that COVID-19 does not only weaken the body—it also confuses and exhausts the immune system itself. NK cells, which should act like sharp virus hunters, become less effective and fail to perform properly.
Understanding these changes may lead to new ways to treat both active infection and lingering complications after recovery.
The study findings were published in the peer reviewed journal: Immuno.
https://www.mdpi.com/2673-5601/5/3/35
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Read Also:
https://www.thailandmedical.news/news/covid-19-news-study-finds-that-sars-cov-2-impairs-natural-killer-nk-cells-functions
https://www.thailandmedical.news/news/tlr2-and-tlr4-are-novel-activating-receptors-for-sars-cov-2-spike-protein-in-nk-cells
https://www.thailandmedical.news/news/breaking-hong-kong-study-finds-that-covid-19-mrna-vaccines-activates-cd57-nk-cells-that-leads-to-acute-myocarditis
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