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Natural Killer Cells May Help Control COVID-19

Dec 14, 2021 10:30:00 AM / by Stacy Matthews Branch, DVM, PhD

AdobeStock_334042834-1Studies that examined NK-cell levels in people with COVID-19 showed that they had decreased levels of NK cells when compared to people who did not have the disease.

Natural killer (NK) cells are capable of killing infected cells without prior activation. Although NK cells do not require antigen stimulation to function, they serve as a robust defense against viral infection. One mechanism used by NK cells to fight viral infection includes the release of granzymes that can trigger pathways leading to the death of infected cells.

Studies that examined NK-cell levels in people with COVID-19 showed that they had decreased levels of NK cells when compared to people who did not have the disease. Rapid decline in SARS-CoV-2 levels were associated with high levels of NK cells early in infection, but the same pattern was not seen with T and B cells. Interestingly, people with moderate to severe COVID-19 illness have dysfunctional NK cells as evidenced by impaired cytotoxic activity in vitro, while NK cells from healthy people effectively killed SARS-CoV-2–infected cells. The difference in NK-cell killing activity in people with moderate to severe illness appears to be associated with impaired target cell binding and release of granzymes. Healthy people and those with mild symptoms of COVID-19 have NK cells that are better able to produce cytokines and chemokines.

Via single-cell RNA sequencing, gene expression patterns of NK cells from people with varying severity of COVID-19 were studied. Gene expression patterns associated with type I interferon signaling control was primarily present in NK cells of people with severe COVID-19 illness. However, an expression pattern consistent with TNF-alpha–controlled signaling was found to be prominent in people with mild forms of the disease. TGF-beta1 impedes NK cell function, and expression patterns associated with TGF-beta1 signaling were increased in people infected with SARS-CoV-2.

Novel treatments involving the use of NK cells may serve as effective antiviral treatments against diseases such as COVID-19. Biomarkers associated with the differential expression of cell-signaling molecules may serve as diagnostic tools to determine the course of the disease and to devise personalized treatment strategies for people with COVID-19 illness. Further investigation regarding the role of NK cells in SARS-CoV-2 and other viral infections can lead to promising effective anti-viral immunotherapies.

People with moderate to severe COVID-19 illness have dysfunctional NK cells as evidenced by impaired cytotoxic activity in vitro, while NK cells from healthy people effectively killed SARS-CoV-2–infected cells. Gene expression patterns associated with type I interferon signaling control were primarily present in NK cells of people with severe COVID-19 illness. One mechanism used by NK cells to fight viral infection includes the release of granzymes that can trigger pathways leading to the death of infected cells. If you would like to learn more about purchasing NK cells to further your medical research, contact Hemacare today!

Reference:

Narni-Mancinelli, E., & Vivier, E. (2021). Clues that natural killer cells help to control COVID. Nature, 600(7888), 226-227. doi: 10.1038/d41586-021-02778-y

Topics: NK Cells

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