Background. The concept of the formation of immunological tolerance is a promising direction for correcting the renal transplant rejection. One of these methods is extracorporeal photochemotherapy (ECP), however, according to the literature, there is no single concept of its mechanisms of action in the formation of immunological tolerance in transplantology.
Aim: To assess the effect of the preventive use of extracorporeal photochemotherapy on the factors of cellular immunity that contribute to the development of long-term tolerance in patients after kidney transplantation.
Materials and methods. A total of 24 patients after a cadaveric kidney transplantation with group matching were included in the study. During the first six months after transplantation, 15 patients of the main group (MG) underwent 10 sessions of ECP in combination with the standard immunosuppression protocol, and 9 patients of the control group (CG) received only standard immunosuppressive therapy. Immunological studies were carried out by the 3rd year after transplantation. The number of cells expressing the antigens CD3, CD4, CD8, CD19, CD16 and CD56, the expression of co-stimulating molecules CD25, CD28 on T-lymphocytes, the number of T-regulatory cells with the CD3+ CD4+ CD25+ (hi) CD127– phenotype was evaluated.
Results. Compared with early post-transplant period, the number of naive CD3+CD4+CD45RO-CD28+ T-cells and CD28+ antigen expression was not different between two groups by 3 years after transplantation and with a group of otherwise healthy individuals (p=0.47 and p=0.26, respectively). Three years after transplantation, the T-helper lymphocyte count (CD3+CD4+) in MG were significantly higher than in CG (48.5±7.3% vs. 43.0±4.6%, respectively; p=0,04), cytotoxic T-lymphocytes count (CD3+CD8+) was 29.5±8.9% in MG, compared to 36.1±8.6% in CG (p=0.09), the ratio of CD4+/CD8+ in MG was significantly higher (1.83±0.72) than in CG (1.29±0.49) (p=0.04). CD19+ lymphocytes count was significantly below normal values in both groups, but in the CG it was more pronounced than in the MG (5.06±2.1% and 7.73±3%, respectively, (p=0.02) In the long-term period, CD3+CD4+CD25+(hi)CD127- T-regulatory cells count in MG was significantly higher than in CG (20.6±10.76*106/L and 12.9±4.97*106/l, respectively)
(p=0.04).
Conclusion. ECP initiates immunological tolerance through the activation of a second co-activation pathway between B-7 and CTLA-4 molecules in the early period after kidney transplantation. As a result, a clone of tolerogenic CD3+CD4+ T-lymphocytes is formed, which differentiates into T-regulatory cells and maintains immunological tolerance in the long-term period. Using ECP as a part of combination therapy allows to normalize the indicators of cellular immunity in the long-term period.Background. The concept of the formation of immunological tolerance is a promising direction for correcting the renal transplant rejection. One of these methods is extracorporeal photochemotherapy (ECP), however, according to the literature, there is no single concept of its mechanisms of action in the formation of immunological tolerance in transplantology.
Aim: To assess the effect of the preventive use of extracorporeal photochemotherapy on the factors of cellular immunity that contribute to the development of long-term tolerance in patients after kidney transplantation.
Materials and methods. A total of 24 patients after a cadaveric kidney transplantation with group matching were included in the study. During the first six months after transplantation, 15 patients of the main group (MG) underwent 10 sessions of ECP in combination with the standard immunosuppression protocol, and 9 patients of the control group (CG) received only standard immunosuppressive therapy. Immunological studies were carried out by the 3rd year after transplantation. The number of cells expressing the antigens CD3, CD4, CD8, CD19, CD16 and CD56, the expression of co-stimulating molecules CD25, CD28 on T-lymphocytes, the number of T-regulatory cells with the CD3+ CD4+ CD25+ (hi) CD127– phenotype was evaluated.
Results. Compared with early post-transplant period, the number of naive CD3+CD4+CD45RO-CD28+ T-cells and CD28+ antigen expression was not different between two groups by 3 years after transplantation and with a group of otherwise healthy individuals (p=0.47 and p=0.26, respectively). Three years after transplantation, the T-helper lymphocyte count (CD3+CD4+) in MG were significantly higher than in CG (48.5±7.3% vs. 43.0±4.6%, respectively; p=0,04), cytotoxic T-lymphocytes count (CD3+CD8+) was 29.5±8.9% in MG, compared to 36.1±8.6% in CG (p=0.09), the ratio of CD4+/CD8+ in MG was significantly higher (1.83±0.72) than in CG (1.29±0.49) (p=0.04). CD19+ lymphocytes count was significantly below normal values in both groups, but in the CG it was more pronounced than in the MG (5.06±2.1% and 7.73±3%, respectively, (p=0.02) In the long-term period, CD3+CD4+CD25+(hi)CD127- T-regulatory cells count in MG was significantly higher than in CG (20.6±10.76*106/L and 12.9±4.97*106/l, respectively)
(p=0.04).
Conclusion. ECP initiates immunological tolerance through the activation of a second co-activation pathway between B-7 and CTLA-4 molecules in the early period after kidney transplantation. As a result, a clone of tolerogenic CD3+CD4+ T-lymphocytes is formed, which differentiates into T-regulatory cells and maintains immunological tolerance in the long-term period. Using ECP as a part of combination therapy allows to normalize the indicators of cellular immunity in the long-term period.

Keywords: immunomonitoring, extracorporeal photopheresis, kidney transplantation