Tumor T_reg cells

Regulatory T cells (T_reg cells) can potently suppress antitumor responses. In the Journal of Clinical Investigation, Mempel and colleagues track the movement and activity of T_reg cells and cytotoxic T lymphocytes (CTLs) in tumors to determine where and how T_reg cells attenuate effector responses. T_reg cells require both priming in the tumor-draining lymph node and exposure to antigen in the tumor microenvironment to be able to suppress CTLs. T_reg cells suppress CTLs in the tumor itself, and this results in the acquisition of an 'exhausted', PD-1⁺TIM-3⁺, functionally impaired phenotype by the CTLs. Although T_reg cells can interact directly with CTLs, their suppressive effect seems instead to operate via downregation of the expression of costimulatory molecules by dendritic cells (DCs), which turns the DCs into poor activators of CTLs. Therefore, T_reg cells alter the balance of stimulatory molecules in the tumor microenvironment to impair the effector function of CTLs.

J. Clin. Invest. (19 May 2014) doi:10.1172/JCI66375