According to a recent study published in journal Nature, the Covid-19 (SARS-CoV-2) virus can infect certain kinds of immune cells called monocytes and macrophages triggering inflammation. The paper writes:

Infected cells undergo inflammatory cell death (pyroptosis) mediated by activation of NLRP3 and AIM2 inflammasomes, caspase-1 and GSDMD. Moreover, tissue-resident macrophages, but not infected epithelial and endothelial cells, from COVID-19 lung autopsies have activated inflammasomes. These findings taken together suggest that antibody-mediated SARS-CoV-2 uptake by monocytes/macrophages triggers inflammatory cell death that aborts production of infectious virus but causes systemic inflammation that contributes to COVID-19 pathogenesis.

Reporting about this finding, CNN Health explains the process further:

Monocytes and macrophages are white blood cells, and they are frontline workers of the immune system. Their job is to circulate in the blood and tissues, to find and destroy pathogens. They do this by eating — or really, surrounding and absorbing — threats like viruses to keep them from being able to infect other cells.

Once a bad actor is absorbed, these cells have what can best be described as a cellular garbage disposal, called an endosome, that normally shuts the infectious agent down.

In the case of the SARS-CoV-2 virus, however, that doesn’t happen. The virus gets out of the endosome and escapes into the body of the cell, where it starts making copies of itself.

The viruses not only get taken up, but once they get taken up, the virus starts replicating, so that was surprising.

– Dr. Judith Lieberman, a pediatric immunologist at Boston Children’s Hospital, who led the research (source: CNN Health)

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Dr Lieberman told CNN Health “When cells die by pyroptosis, they release all kinds of inflammatory proteins that cause fever and summon more immune cells to the site.”

“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,” Dr Lieberman added.

“All the patients we studied had signs of respiratory distress and pneumonia. The ones who had [SARS-CoV-2] had many more of these inflammasomes and dying cells. So it’s likely that [SARS-CoV-2] is particularly good at inducing it, but we don’t know why.”