Role of the cells of the system of mononuclear phagocytes and regulatory T-lymphocytes in the formation of the state of immunosuppression in sepsis

Sepsis still represents one of the leading causes of death in hospitalized patients worldwide, and its incidence is increasing. Changes in the relative and absolute blood levels of monocytes, dendritic cells, myeloid suppressor cells, and regulatory T-lymphocytes in the blood of patients with sepsis and septic shock were studied on the 3rd–4th day after diagnosis in order to identify the stage of immunosuppression. 33 patients with sepsis (19 men and 14 women, age 57.1 ± 19.9 years) and 6 patients with septic shock (2 men and 4 women, age 49.3 ± 19.6 years) were examined. The control group included 30 healthy donors. Subpopulations of monocytes, dendritic cells, myeloid suppressor cells, and Treg cells were determined by flow cytometry. A significant decrease in HLA-DR expression on monocytes, a decrease in the relative content of classical monocytes, myeloid and plasmacytoid dendritic cells, an increase in the percentage of intermediate monocytes and G-MLSC CD15+, an increase in the absolute content of Treg cells in patients with sepsis and septic shock were revealed. The revealed functional defects and shifts in the composition of the leukocyte population indicate the development of the stage of immunosuppression in patients with sepsis.