Reconstructive immunomodulation under the influence of thymic hexapeptide of number and phenotype of subsets CD16<sup>+</sup>CD62L<sup>+</sup>CD11b<sup>+</sup>CD63<sup>-</sup> and CD16<sup>+</s

Dysfunction of neutrophilic granulocytes (NG) is a decisive factor in the development and progression of atypical purulent-inflammatory diseases, including acute destructive pneumonia (ADP) in children. A promising approach is to include immunocorrective therapy in complex treatment, thus promoting recovery of NG functions. The objective of this study was to assess the features of defective NG functioning associated with changes in relative contents and phenotype of CD16+CD62L+CD11b+CD63- and CD16+CD62L+CD11b+CD63+ neutrophil subsets in children with ADP, to evaluate clinical and immunological effectiveness of immunomodulatory therapy in complex postoperative treatment using a pharmaceutical drug with a synthetic thymic hexapeptide (pdHP) being the active substance. The study included 21 children aged 2-4 years: with a diagnosis of ADP (study group, SG) before complex treatment, and a group after treatment with hexapeptide (SG1). The comparison group included 20 conditionally healthy children (CG), Twenty children treated for ADP comprised the archival comparison group (aCG). The functions of NG were assessed by the content of CD16+CD62L+CD11b+CD63- and CD16+CD62L+CD11b+CD63+ subsets using FC500 (Beckman Coulter) device. We also determined indices characterizing phagocytosis (%PAN, PN, PI, %D, ID), NADPH oxidase activity (%PPC, MCI) in the NBT test. We have found a phenotypic transformation of physiological subset to CD16dimCD62LdimCD11bbrightCD63- NG with defective immune properties, a 3-fold increase in the content of NG subset with hyperactivated phenotype CD16brightCD62LbrightCD11bbrightCD63bright (p 0.05), a defect in phagocytic function, but increased oxidase activity (p1, 2 0.05) in immunocompromised children with ADP. After complex treatment with the inclusion of hexapeptide, we observed normalization of NG effector functions associated with phenotype remodeling and restoration of the subpopulation ratio. Positive clinical dynamics was revealed when compared with aCG children receiving conventional therapy, i.e., a significant reduction in fever duration (|δ| = 0.98), respiratory failure (|δ| = 0.99), more rapid regression of pleural effusion (|δ| = 0.96) and early removal of drainages (|δ| = 1.00). The obtained results indicate a pronounced positive clinical and immunological efficiency of pdHP usage in complex treatment of children with ADP.