Programmed-death-1 (PD-1) is a surface receptor expressed on activated
and exhausted effector T cells, whichmediate T cell inhibition
upon binding with its ligand, the PD-L1. PD-L1 is expressed on a variety
of tumor cells and other cellular components of the tumor microenvironment.
Blocking the PD-1/PD-L1 pathway by selective blocking
antibodies was shown to restore the function of tumor-specific CD4+
or CD8+ cells both in mouse and human studies