The Relationship Between the PD-1/PD-L1, Th17 and Treg Cells in Cancer Immunity

ABSTRACT

Programmed cell death 1 (PD-1) and its ligand PD-L1 (programmed death 1 ligand 1) are important immune checkpoints, and their interaction negatively regulates effector T-cell activation and proliferation, as well as being an important pathway for tumor cells to evade immune surveillance. Blocking the binding of PD-1 to PD-L1 can relieve the inhibition of T cells by tumor cells or antigen-presenting cells, and restore their ability to recognize and kill tumor cells. However, PD-1/PD-L1 is complexly regulated and varies among tumors, occurring mainly at the genetic, transcriptional and post-transcriptional levels. In the last decade, immune checkpoints blocker has become an important part of the treatment for many malignant tumors, resulting in longer tumor remission. While achieving better efficacy, the blocking effect in solid malignancies is still deficient, which may be related to the complex tumor microenvironment. As important parts in the tumor microenvironment, Tregs and Th17 cells have been shown to be involved in tumor development. Currently, the complex relationship between the PD-1/PD-L1 pathway, Tregs and Th17 cells has not been fully elucidated. In this paper, we review the interaction between the PD-1/PD-L1 pathway, Tregs and Th17 cells, with the aim of providing new ideas for future tumor therapy. cells, can bind to PD-1 receptors on the surface of T cells