MO1005: Analysis of Expression of Immune System Genes that are Responsible for Activation and Inhibition of T-Cell Immune Response in Renal Transplant Recipients after Extracorporeal Photochemotherapy

Abstract

Abstract BACKGROUND AND AIMS Due to the increasing need for kidney transplantation, there is a demand for new methods of preventing rejection of the transplant based on the mechanisms of natural regulation of the immune response. Extracorporeal photopheresis (ECP) is one of these technologies whose clinical efficacy in the prevention and treatment of acute renal transplant rejection has been confirmed by many studies, but the mechanism of its effect has not been fully understood. Characterization of the genes responsible for the activation and inhibition of the immune response during ECP is an important step towards the modification of immunosuppressive therapy. The aim of this study was to analyze the changes in the expression level of the genes responsible for the activation and inhibition of the T-cell response in the recipients of the renal graft after ECP. METHOD An open cohort randomized trial was conducted with 20 patients who underwent a single group cadaver kidney transplantation from an unrelated donor. The recipients of the compared groups received standard immunosuppressive therapy and the same therapy in combination with ECP procedures, according to the study protocol. Each recipient of the main group received 15 sessions of ECP within 6 months. The level of gene expression was analyzed by real-time RT-PCR. Comparison of the study groups was carried out at point 1 (1st–4th day) and 2 (30th day). RESULTS The analysis of clinical data did not show statistically significant clinical differences, but in the specific consideration of each pair of cases, the tendency to some improvement in the transplant organ engraftment rate in the early terms after the transplant, and better survival of the graft and the recipient was revealed. For instance, patients of the main group revealed no transplant rejection by clinical laboratory signs as well as the results of histological examination of biopsy specimens. In the comparison group, acute graft rejection was clinically diagnosed and was confirmed by histological examination as humoral type rejection. The level of expression of genes involved in immune response regulation (CD28, CTLA4, PDL1 and FOXP3) and cytokine genes (TNFA, IL1, IL2, IL10 and IFNG) in the studied groups was determined. A decrease in the level of expression of the genes for the proinflammatory cytokines IL1, IL2 and IFNG was noted by the 30th day after transplantation. At the same time, the expression of the genes PDL1 and FOXP3, which regulate the development of the regulatory response, significantly increased by the 30th day after transplantation. Correlations of the level of gene expression with the presence/absence of rejection episodes have not been established. To assess the effect of the ECP on these gene expression, a comparison was made of the level sof transcript representation of patients receiving standard immunotherapy and immunotherapy in combination with ECP, and a significant increase in the expression of PDL1 and FOXP3 genes (Fig. 1A and B) was found in the group of patients who underwent ECP procedures (P = .0009 and .0013, respectively). CONCLUSION According to the results of comparative analysis, the level of expression of pro-inflammatory cytokines' genes IL1, IL2 and IFNG decreased to the 30th day after transplantation. A 30-day comparison between groups shows an increase in the expression level of the PDL1 and FOXP3 genes. Increased expression of these genes may be associated with the activation of regulatory T-cells and the development of peripheral tolerance and can become a criterion for the modification of immunosuppressive therapy.