ORIGINAL RESEARCH article
Front. Cell. Infect. Microbiol.
Sec. Virus and Host
Volume 15 - 2025 | doi: 10.3389/fcimb.2025.1635043
This article is part of the Research TopicViral Pathogenesis and Host Defense: Understanding the Missing Links to Combat DiseaseView all 7 articles
The Effect of COVID-19 and Sex Differences on Natural Killer Cell Cytotoxicity
Provisionally accepted- 1Department of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- 2Snyder Institute for Chronic Diseases of Canada, University of Calgary, Calgery, Alberta, Canada
- 3Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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COVID-19 has caused more than 7 million deaths worldwide, and according to the World Health Organization, it continues to result in more than 1000 reported deaths per month at the time of this writing. It is crucial to understand the immune response to COVID-19 since the virus continues to persist. Natural killer (NK) cells play a critical role in the immune defence against viral infections, including COVID-19. While it is well documented that infected patients have a reduction in lymphocytes and NK cells, gaps in knowledge exist regarding the function of NK cells. To study the function of NK cells in patients hospitalized with COVID-19, peripheral blood was obtained from patients admitted to the medical (non-ICU) wards at a large tertiary hospital. We demonstrated a decrease in the mature cytotoxic subset of NK cells within the peripheral blood of patients hospitalized with COVID-19. We also observed a notable reduction in the cytotoxic function of NK cells against tumour targets. We examined the mechanisms leading to NK cell killing. We found reductions in the intracellular levels of effector molecules, the degranulation of cytotoxic granules, and the extracellular concentrations of released effector molecules. We identified dysfunctional intracellular granule trafficking required to position the granules for degranulation, which would be consistent with the reduced release of effector molecules. We found clusters of inhibitory receptors were upregulated in subsets of NK cells, in keeping with inhibition of cytotoxicity. Additionally, males with COVID-19 showed NK cell defects compared to healthy males, while no significant differences were observed in females. Our findings highlight defects in cytolytic effector molecules, granule trafficking and release, and increased expression of inhibitory receptors on NK cells in patients hospitalized with COVID-19, in addition to a sex difference in cytolytic function, which contributes to defective NK cell function in COVID-19.
Keywords: COVID-19, effector molecules, granule trafficking, Natural killer (Nk) cell, cellular cytotoxicity, immunology, sex differences, SARS-CoV-2
Received: 25 May 2025; Accepted: 05 Sep 2025.
Copyright: © 2025 Dagar, Polyak, Mok, Feehan, Potemkin, Tremblay and Mody. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Christopher H. Mody, Department of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, T2N 1N4, Alberta, Canada
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