The role of T_reg cells in the cancer immunological response

Problem statement: T cell-mediated immunosuppression has been observed for decades without clarification as to which factor was responsible for this observation. The identification of CD4⁺CD25⁺ regulatory T (T_reg) cells represents a milestone in the filed of immunology and provides an explanation for T-cell-mediated immunosuppression. Although T_reg cells were originally identified for their ability to prevent organ-specific autoimmune disease in mice, emerging evidence suggests that T_reg cells play a pivotal role in tumor immunity and contribute to tumor growth and progression, thereby having an important impact on the outcome of cancer patients. Approach: This article reviewed the medical literature to describe how T_reg cells affect anti-tumor immunity. Results: T_reg cells suppressed anti-tumor immunity by inhibiting the effector functions of tumor-specific T cells and NK cells. Importantly, tumor cells played an active role in recruiting and generating T_reg cells and creating a suppressive tumor microenvironment. Strategies to deplete T_reg cells or inhibit their function had yielded promising results by enhancing anti-tumor immunity in experimental studies as well as clinical practice. Conclusion: A better understanding of the pathophysiology of T_reg cells not only increased our knowledge in a variety of aspects of immunology but also potentially benefited cancer patients.