The role of regulatory T cells in the modulation of anti-tumor immune response

Abstract

Regulatory T cells (T<inf>reg</inf>) represent a subset of CD4⁺T{cyrillic} cells whose function is to suppress immune responses. T<inf>reg</inf> lymphocytes can be divided into two subsets: natural nT<inf>reg</inf> lymphocytes that are developed in the thymus and inducible iT<inf>reg</inf> lymphocytes, which originate from conventional T lymphocytes on the periphery. The majority of T<inf>reg</inf> lymphocytes express high levels of interleukin-2 (IL-2) receptor α chain (CD25) and transcription factor FoxP3 (critical for the development and suppressor activity of iT<inf>reg</inf> lymphocytes). Cancer cells can modulate anti-tumor immune response indirectly, through the activation of T<inf>reg</inf> lymphocytes. It has been shown that the loss of regulatory function by depletion of tumor-induced T<inf>reg</inf> lymphocytes may enhance effectors response, resulting in tumor rejection, while the increased number of Treg lymphocytes effectively prevents tumor destruction. nT<inf>reg</inf> lymphocytes express increasingly CTLA-4 and membranebound TGF-β, which inhibits cytokine production and responses of effectors lymphocytes. iT<inf>reg</inf> lymphocytes secrete immunosuppressive cytokines such as IL-10 and TGF-β. T<inf>reg</inf> lymphocytes represent one of important obstruction in anti-tumor immunity.