MODULATING EFFECTS OF SYNTHETIC THYMIC HEXAPEPTIDE IN AN IN VITRO EXPERIMENT ON SUBSETS CD66B+CD16+CD11B+CD11C- AND CD66B+CD16+CD11B+CD11C+ NEUTROPHIL GRANULOCYTES FROM HEALTHY CHILDREN AND CHILDREN WITH ACUTE DESTRUCTIVE PNEUMONIA COMPLICATED BY SEPSIS

Neutrophil granulocyte (NG) functional disorders can lead to the severe or course of purulent-inflammatory diseases (PID). The use of immunomodulatory substances can change the level of NG receptor expression and improve their functional activity. Research of studied NG subsets CD66b⁺CD16⁺CD11b⁺CD11c^- and CD66b⁺CD16⁺CD11b⁺CD11c⁺ impairments, NG effector functions and the effect of immunomodulatory substances on them in children with PID can serve as a basis for development of diagnostic tools and new immunotherapeutic approaches.

Objective: to clarify the modulatory effects of a synthetic thymic hexapeptide (HP) on the subsets of CD66b⁺CD16⁺CD11b⁺CD11c^- and CD66b⁺CD16⁺CD11b⁺CD11c⁺ neutrophilic granulocytes in vitro system in healthy children and children with acute destructive pneumonia complicated by sepsis (ADP-s).

Materials and methods: peripheral blood (PB) samples of children aged 2-5 years were studied: with ADP-s (n=12), the study group (SG), and healthy children (n=17),  the comparison group (CG). The samples were incubated with HP (10^-6 g/l, 60 min, T=37°C) - SG1, CG1. The following parameters were determined: the number of CD66b⁺CD16⁺CD11b⁺CD11c^- and CD66b⁺CD16⁺CD11b⁺CD11c⁺ NG subsets, the MFI of molecules, NADPH-oxidase activity in the NBT test, and the number of NETs in PB smears.

Results: Two NG subsets CD66b⁺CD16⁺CD11b⁺CD11c^- and CD66b⁺CD16⁺CD11b⁺CD11c⁺ were detected in SG and CG. The SG showed 4,5-fold increase in CD66b⁺CD16⁺CD11b⁺CD11c⁺NG subset, 5,5-fold decrease in CD66b⁺CD16⁺CD11b⁺CD11c^-NG subset (p_1,2<0.05), lower MFI of receptors in both subsets relative to CG, presence of NETs.  Also, in SG, an increase in %PhPCsp and MCIsp and a decrease in these indicators after S.aureus treatment were established, which indicates the depletion of oxidase reserves (p_1,2<0.05). Incubation with HP did not affect the NG content and phenotype of the studied subsets in CG1. In SG1, the effects of HP were manifested in 6-fold increase in the proportion of the CD66b⁺CD16⁺CD11b⁺CD11c^-NG subset, a 5-fold decrease in the proportion of the CD66b⁺CD16⁺CD11b⁺CD11c⁺NG subset (p<0.05), restoration of oxidase activity and a decrease in the number of NETs.

Conclusion. The obtained data confirm the immunomodulatory effect of HP in vitro, testify to the positive effect on the studied NG subsets, accompanied by the restoration of the microbicidal activity of NG in children with ADP-s and can be translated into clinical practice.