ROLE OF T-CELL SUBPOPULATIONS IN THE IMMUNOLOGIC TOLERANCE INDUCTION
One of the main problems of modern transplantation is a necessity maintain immunodeficiency to prevent graft rejection. Long-term drugs designed to reduce the level of immunoreactivity, eventually leads to serious infectious diseases and cancer. Consequently approaches to reduce donor-specific effector responses without affect the immune response against other antigens are developed. There are several types of regulatory cells in humans including CD4+ T-regulatory cells (Treg), and a number of T-lymphocytes (CD8+CD28- T cells, CD4-CD8- T cells). All Tregs perform regulatory function against effector cells during the inflammatory response by using similar nonspecific mechanisms. These mechanisms are mediated either through surface molecules (such as CTLA-4 or PD-1/PD-L1) or soluble molecules (such as IL-10, TGF-β, IDO). However, there is evidence of action of Tregs through the antigen-specific mechanism. Understanding principles of the alloantigen-specific immunological tolerance formation of Treg can create prerequisites for the cellular approaches development aimed at reducing the level of immunodeficiency necessary for donor tissue long-term functioning. This review summarizes the current evidence on the various populations and the using mechanisms of regulatory T cells to induce immunological tolerance.