Regulatory T cell: a protection for tumour cells

•  Introduction •  The mechanisms of Tregs stimulating metastasis and mediating immunosuppression      ‐   Tregs stimulate cancer metastasis through RANKL‐RANK signal      ‐   TGF‐b inhibits anti‐tumour immunity in tumour    microenvironment      ‐   Immunosuppression of Tregs can be abolished by neutralized    or knocked out IL‐10      ‐   CTLA‐4 participates in the suppression of Tregs      ‐   Blocking GITR weakens the immunosuppression of Tregs      ‐   Others •  The manners of Tregs in tumour stroma      ‐   Tregs proliferate in tumour microenvironment      ‐   Tumours secrete chemokines recruiting Tregs from    peripheral blood      ‐   Non‐regulatory T cells converse into Tregs in tumour stroma •  The target cells of Tregs in tumour microenvironment      ‐   Tregs weaken body immune surveillance by inhibiting DCs      ‐   Tregs suppress non‐regulatory CD4+ T cells      ‐   Tregs inhibit the proliferation and anti‐tumour capacity    of CD8+ T cells      ‐  Tregs suppress the lysis of NK cells      ‐   Tregs inhibit the proliferation of B cells      ‐   Tregs inhibit function of macrophage directly •  A new immunotherapeutic target      ‐   Depletion of Tregs leads to tumour regression      ‐   Inhibiting the immunosuppression of Tregs improves    the prognosis of cancer patients      ‐   Combination immunotherapy may be the best choice •  ConclusionsCharacterized by immunosuppression regulatory T cells (Tregs) play a key role in maintaining immune tolerance. A growing number of tumours have been found with Tregs accumulating in microenvironment and patients with high density of Tregs in tumour stroma get a worse prognosis, which suggests that Tregs may inhibit anti‐tumour immunity in stroma, resulting in a poor prognosis. In this paper, we demonstrate the accumulation of Tregs in tumour stroma and the possible suppressive mechanisms. We also state the immunotherapy that has being used in animal and clinical trials.