COVID-19 Immunology: Swedish Study Shows Natural Killer Cell Immunotypes Linked To COVID-19 Disease Severity
: Researchers from Karolinska Institutet-Sweden in a new study have discovered that so-called natural killer (NK) cells were strongly activated early after SARS-CoV-2 infection but that the type of activation differed in patients with moderate and severe COVID-19.
This new discovery brings researchers one step closer toward understanding how the immune system contributes to severe COVID-19.
The research findings were published in the journal: Science Immunology. https://immunology.sciencemag.org/content/5/50/eabd6832
The findings also help to contribute to current understanding of development of hyperinflammation in some patients.
It has been seen that SARS-CoV-2 infection can in some cases cause severe COVID-19 disease. Although this is thought to be partially driven by a misdirected innate immune response, many aspects of the early immune response to the infection remain elusive.
The researchers from Karolinska Institutet have now, in collaboration with colleagues at the Karolinska University Hospital, investigated the early response to SARS-CoV-2 infection by NK cells, a cell type in the immune system known to be important in the control of viral infections.
The research analyzed blood samples from 27 patients with moderate (10) and severe (17) COVID-19 infection.
The study team also included blood samples from 17 healthy individuals as a control group. The result showed that NK cells were strongly activated in the blood shortly after infection.
Dr Niklas Björkström, physician and immunology researcher at the Center for Infectious Medicine, Department of Medicine Huddinge, at Karolinska Institutet, who led the study told Thailand Medical News, "The type of NK cell activation detected differed considerably in patients with moderate compared to severe disease.”
The study team said that it is likely that the type of NK cell response observed in SARS-CoV-2 infected patients with moderate disease is a canonical NK cell response shared between many types of viral infections, according to the researchers.
Patients who developed severe COVID-19 however had a different composition of responding NK cells. These patients' NK cells generally had higher expression of the proteins perforin, NKG2C and Ksp37, which according to the researchers reflect a high presence of so-called adaptive NK cells.
It is known that adaptive NK cells have an even greater ability to kill target cells compared to other NK cells.
The study team is now investigating to what extent the NK cell-mediated immune response observed in the critically ill patients might contribute to COVID-19 severity, and the extent to which other parts of the response may be beneficial.
Dr Björkström added, "Taken together, the study findings provide additional insights into immune reactions in early SARS-CoV-2 infection and ensuing COVID-19 disease. We hope that these insights will contribute to the improved care and treatment of
patients with severe COVID-19 disease."
The research is part of the larger Karolinska COVID-19 Immune Atlas project, which aims to increase knowledge about the characteristics of immune cells in patients with COVID-19.The project is ongoing.
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