Analysis of regulatory T lymphocytes in patients with traumatic brain injury

In recent years, traumatic brain injury (TBI) has been one of the most urgent medical and social problems due to its prevalence, predominantly affecting young people of working age, causing high mortality, disability and economic costs for treatment and subsequent rehabilitation of patients. At present, the role of patients’ immune system in evolving neuroinflammation after traumatic brain injury has been proven. Treg cell populations represent an important factor determining the outcome of the disease due to promoting induction of immunological tolerance, being a significant component of immunoregulation. As a result of our study, we found a decrease in the relative content of Treg within the total lymphocyte pool of peripheral blood, which has the CD3⁺CD4⁺CD25^bright phenotype in patients of the 3^rd and 4^th groups, in comparison with the data from control group. Moreover, a decreased relative content of Tregs (CD4⁺CD25⁺T cells) was revealed which is due to the degree of brain tissue damage and, as a result, their migration to suppress inflammation due to production of anti-inflammatory cytokines (TGF-â, IL-10). The Treg population is heterogeneous, thus prompting us for analysis of the Treg subpopulations profile based on the expression of CD45R0 and CD62L. When assessing subpopulations of regulatory T lymphocytes within CD45Ro and CD62L, significant changes were found only in patients with brain contusion. The changes were revealed within the pool of “naive” T regulatory lymphocytes with the CD3⁺CD4⁺CD25^brightCD39⁺ Treg phenotype, capable of producing a wide range of cytokines specific for Th1, Th2, Th17, in patients with mild, moderate and severe TBI. Meanwhile, the level of highly active CD3⁺CD4⁺CD25^brightCD73⁺ Tregs was significantly reduced in patients with moderate and severe TBI. These changes indicate an imbalance in immunoregulatory processes resulting from extensive damage to brain tissues.