Aim. To characterize parameters of neutrophil extracellular trap (NET) production in the leukocyte culture and citrullinated histone H3 (citH3) level in peripheral blood to assess the features of NETosis in children with tuberculosis.Materials and methods. The study included 20 children with active pulmonary tuberculosis (TB group) and 20 clinically healthy children without signs of sensitization to Mycobacterium tuberculosis antigens (control group). The ability of neutrophils to form NETs under ex vivo exposure to a non-specific immune stimulant and the concentration of citH3 in peripheral blood were investigated.Results. Neutrophils in children with tuberculosis formed filamentous NETs (Me = 21.0 and Me = 16.0, respectively; p = 0.0474) and cloud-like NETs (Me = 10.5 and Me = 4.0, respectively; p = 0.0068) more frequently than the controls. Filamentous NETs prevailed in both groups. However, cloud-like NETs were registered in all patients in the TB group (100%) and only in 15 of 20 children in the control group (χ2 = 16.01; p < 0.0068). The concentration of citH3 in the blood was 18.9 times higher in the TB group than in the control group (Me = 26.5 and Me = 1.4, respectively; p = 0.0041). A strong positive correlation was found between the citH3 concentration and the generation of filamentous (r = 0.86; p = 0.0137), but not cloud-like NETs (r = 0.95; p = 0.0008) in both groups.Conclusion. The high level of citH3 in the TB group can reflect its NETosis-induced release and be caused by increased NETosis in vivo. This may be due to the previously formed potential of neutrophils to generate NETs (a proNETotic phenotype), which is consistent with our observation of an increased ability of isolated neutrophils to form extracellular traps ex vivo in children of the TB group.
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