Factor V is an immune inhibitor that is expressed at increased levels in leukocytes of patients with severe Covid-19



8th February 2021

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This research has not been peer-reviewed, and has been posted on pre-print repository medRxiv. This is a preliminary report that should not be regarded as conclusive, guide clinical practice/health-related behaviour, or be reported in news media as established information.


Severe Covid-19 is associated with elevated plasma Factor V (FV) and increased risk of thromboembolism. We report that neutrophils, T regulatory cells (Tregs), and monocytes from patients with severe Covid-19 express FV, and expression correlates with T cell lymphopenia. In vitro full length FV, but not FV activated by thrombin cleavage, suppresses T cell proliferation. Increased and prolonged FV expression by cells of the innate and adaptive immune systems may contribute to lymphopenia in severe Covid-19. Activation by thrombin destroys the immunosuppressive properties of FV. Anticoagulation in Covid-19 patients may have the unintended consequence of suppressing the adaptive immune system.

Author list:

Jun Wang, Prasanti Kotagiri, Paul A Lyons, Federica Mescia, Laura Bergamaschi, Lorinda Turner, Rafia S Al-Lamki, Michael D Morgan, Fernando J Calero-Nieto, Karsten Bach, Nicole Mende, Nicola K Wilson, Emily R Watts, Cambridge Institute of Therapeutic Immunology and Infectious Disease-National Institute of Health Research (CITIID-NIHR) COVID BioResource Collaboration, Patrick F Chinnery, Nathalie Kingston, Sofia Papadia, Kathleen Stirrups, Neil Walker, Ravindra K Gupta, Mark Toshner, Michael P Weekes, James A Nathan,  Sarah R Walmsley, Willem H Ouwehand, Mary Kasanicki, Berthold Göttgens, John C Marioni, Kenneth GC Smith, Jordan S Pober, John R Bradley