Regulatory T cells and EBV associated malignancies.

It has been shown that the T-regulatory cells (Tregs) not only play a key role in the establishment and maintenance of peripheral tolerance to prevent the autoimmune disease, but also inhibit the anti-tumor immunity. Recently, many studies have demonstrated that cytotoxicity T cells (CTL) can control the growth of EBV-positive tumor cells in vitro, including Hodgkin's lymphoma (HL), nasopharyngeal carcinoma, posttransplantation lymphoproliferative disorders (PTLD), depending on the large mount of EBV antigens presented by MHC molecules on the surface of these malignant cells. However, limited benefit of CTL adoptive immunotherapy has been reported in the treatment of EBV positive HL and NPC, and Tregs are regarded as a critical hurdle in this issue. In the present review, we discuss the correlation of EBV antigens expression in the tumor cells and the induction of Tregs in tumor microenvironment. Treg subsets and its possible mechanism to attenuate the anti-tumor immunity in EBV associated malignancies are also discussed, following by the possible strategies of targeting Tregs in the future immunotherapy for EBV positive cancers.