Systemic and local effective function of neutrophilic granulocytes associated with transformation of the phenotype of their functionally significant subset in children with small purulent infection

Defects in the functioning of neutrophilic granulocytes (NG) are accompanied by various purulent-inflammatory diseases that have a persistent-relapsing course. The bactericidal activity of NG, the processes of intracellular and extracellular killing of bacteria, is directly dependent on their phenotypic features: the expression level of functionally significant membrane receptors CD64, CD16, CD32, CD11b triggering effector processes. It was shown that there are subsets of NG with different phenotypic characteristics and the course and outcome of infectious and inflammatory diseases directly depends on their usefulness. Despite the large amount of accumulated information, the question of the transformation of NG subpopulations phenotype during NG response formation in children with local purulent processes of soft tissues - a small purulent infection (SPI) remains poorly understood. Purpose: to evaluate the local and systemic effector function of neutrophilic granulocytes (phagocytosis, NET formation) with clarification of the phenotype of functionally significant CD64-CD16+CD32+CD11b+, CD64+CD16+CD32+CD11b+ and CD64-CD16+CD32-CD11b+ NG subpopulations in peripheral blood (PB) in children with SPI. Materials and methods. We evaluated the phagocytic function of NG in 60 PB samples of children 5-9 years old, on the 2-3rd day of acute purulent process, before surgery, in smears - prints taken from the local focus of purulent inflammation and 17 PB samples of conditionally healthy children. Also the ability to form NET was additionally determined in smears-prints in children with SPI. In parallel, in PB we evaluated:% NG simultaneously carrying CD64, CD16, CD32, CD11b receptors and their expression density (MFI) by flow cytometry (CYTOMICS FC500, Beckman Coulter, USA). Statistical data processing was performed in the Microsoft Exel 2016 and Stat Plus 2010 software packages. Nonparametric criteria were used: median (Me) and interquartile range (Q1; Q3), Mann-Whitney U-test and Wilcoxon test. Results . We found a significant increase in the content of the NG subpopulation with a negatively transformed phenotype CD64-CD16+CD32-CD11b+ with defects in the expression of CD64 and CD32 receptors, which is the cause of inadequate inclusion of NG in inflammatory processes, disruption of phagocytic activity at the systemic and local levels and the occurrence of SPI in children. The formation of NET in the first stage is necessary to supplement the effector function of NG in order to compensate for disorders of phagocytosis.