Neutrophil extracellular traps as markers of infectious and aseptic inflammation

One of the important problems of medicine is the search for new reliable markers of inflammation that would allow us to determine the type of inflammatory process. The aim of the study was to identify specific markers of infectious and aseptic inflammation based on the analysis of morphological variants of neutrophil extracellular traps (NETs). The study included 26 patients with various nosological forms of inflammation in the abdominal cavity (12 with acute appendicitis, 8 with acute cholecystitis, 6 with a diagnosis of pancreatitis/ pancreonecrosis) after surgery. The study also included 20 patients with post-COVID and a group of 10 volunteers no clinical manifestations of the disease, but at the same time had contacts with flu patients. Neutrophils were isolated using gradient centrifugation. Fluorescence microscopies with the dye SYBR Green (JSC “Evrogen”, Russia) were used for NET visualization and counting. NETs in the morphological form of neutrophils web structure were found in the blood of surgical patients with acute appendicitis who had a favorable course of the postoperative period. In a group of volunteers who were exposed to influenza but did not have symptoms of an infectious disease, we also found neutrophils web structure. In all patients with abdominal inflammation complicated by abdominal abscess, in addition to neutrophil web structure, abnormal forms of NETs were recorded, in particular, NETs in the form of single filaments. In the post-COVID patients an absolute absence of neutrophilis web structure was revealed. In all post-COVID patients, NETs are found only in the form of single filaments. The results of subsequent experiments showed that collagen peptides are inducers of the formation of NETs in the form of single filaments. The detection of neutrophils web structure is a sign of an infectious inflammatory process. NETs in the morphological form of single filaments are markers of aseptic inflammation, as well as a sign of endothelial damage.