Regulatory T (Treg) cells in cancer: Can Treg cells be a new therapeutic target?

Regulatory T (Treg) cells suppress abnormal/excessive immune responses to self- and nonself-antigens to maintain immune homeostasis. In tumor immunity, Treg cells are involved in tumor development and progression by inhibiting antitumor immunity. There are several Treg cell immune suppressive mechanisms: inhibition of costimulatory signals by CD80 and CD86 expressed by dendritic cells through cytotoxic T-lymphocyte antigen-4, interleukin (IL)-2 consumption by high-affinity IL-2 receptors with high CD25 (IL-2 receptor α-chain) expression, secretion of inhibitory cytokines, metabolic modulation of tryptophan and adenosine, and direct killing of effector T cells. Infiltration of Treg cells into the tumor…