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Since the start of the COVID-19 pandemic, doctors have been trying to figure out why some people with coronavirus develop severe inflammation, which can lead to respiratory distress and damage organs.
A study that was published in Nature and conducted by researchers at Boston Children’s Hospital and Massachusetts General Hospital provides a possible answer.
Researchers determined the coronavirus infects immune cells called monocytes in the blood and macrophages in the lungs. That infection causes the immune cells to “die a fiery death called pyroptosis” and release inflammatory alarm signals, Boston Children’s Hospital said in a news release.
“When cells die by pyroptosis, they release all kinds of inflammatory proteins that cause fever and summon more immune cells to the site,” Judith Lieberman, a pediatric immunologist at Boston Children’s Hospital who led the research, told CNN.
“We don’t have any way of treating that once it gets started. It’s just sort of it’s like a little fire. It spreads and explodes and no fire extinguisher is capable of putting it out.”
Lieberman told CNN the study helps explain why older people and people with underlying health conditions, such as diabetes and obesity, are more likely to become severely ill with COVID, since those conditions already have some inflammation.
“They’re much, much more likely to start these inflammatory fires,” she said. “They have sort of a low slow burn going on anyway. And once it gets started it’s really hard to put out the fire.”
The research team examined blood samples from COVID patients at Massachusetts General Hospital and compared them with blood samples from healthy people and patients with other respiratory illnesses. They also looked at lung autopsy tissue from COVID fatalities.
All the patients had signs of respiratory distress, but COVID patients had more dying cells.
About 6% of blood monocytes found in infected COVID patients died “an inflammatory death,” as did about a quarter of macrophages from the lung tissue, the Boston Children’s Hospital news release said.
The research also indicated antibodies produced by people with COVID may actually help infection and inflammation occur.
Researchers noticed that people with COVID had a higher number of monocytes carrying a receptor called CD16, Boston Children’s Hospital said. Antibodies, which are naturally produced by the body to fight off a virus, attach to the CD16 receptors.
“The antibodies coat the virus,” Lieberman said in the news release. “Then cells with the CD16 receptor take up the virus.”
Fortunately, the researchers found antibodies that healthy people create after taking the Pfizer and Moderna mRNA vaccines did not help the infection of monocytes occur.
Sources
Nature. “FcγR-mediated SARS-CoV-2 infection of monocytes activates inflammation”
Boston Children’s Hospital. “How COVID-19 triggers massive inflammation”
CNN. “Study reveals how Covid-19 infections can set off massive inflammation in the body”
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