Interrelationships between polymorphonuclear leukocytes (PMNs)- neutrophils, blood coagulation system and vascular endothelium during Covid-19 infection

Background. Polymorphonuclear leukocytes (PMNs-neutrophils) influence the processes of inflammation and immunity, participating in phagocytosis, cytoplasmic degranulation, NETosis, generation of reactive oxygen species (ROS), receptor-mediated communications with other cells and systems, innate and adaptive immunity, blood coagulation-and circulatory systems, etc. Neutrophils during development of Covid-19 disease. The participation of neutrophils during development, treatment and management of COVID-19 infection is evaluated and largely discussed in the scientific medical literature. The elevated neutrophil-to-lymphocyte ratio (NLR) and dynamic lowering of some routine blood parameters seem to be critical markers of severe COVID-19. Thus, dysregulation of immune system-with special participation of complement, leads to hyperproduction of cytokines and chemokines („cytokine storm”). The resulting pro-adhesive and prothrombotic effects stimulate further adhesion of leukocytes and platelets to the vascular endothelium, causing macro-and microvascular thromboses, capillary plugging and impaired microvascular flow. © 2022, Bulgarska Akademiya na Naukite. All rights reserved.