Regulatory T Cells in the Tumor Microenvironment.

Regulatory T cells (T _regs ) are an immunosuppressive subpopulation of CD4 ⁺ T cells that are endowed with potent suppressive activity and function to limit immune activation and maintain homeostasis. These cells are identified by the hallmark transcription factor FOXP3 and the high-affinity interleukin-2 (IL-2) receptor chain CD25. T _regs can be recruited to and persist within the tumor microenvironment (TME), acting as a potent barrier to effective antitumor immunity. This chapter will discuss [i] the history and hallmarks of T _regs ; [ii] the recruitment, development, and persistence of T _regs within the TME; [iii] T _reg function within TME; asnd [iv] the therapeutic targeting of T _regs in the clinic. This chapter will conclude with a discussion of likely trends and future directions.