PDCD1LG2 and cancer: In the tumor microenvironment, the interaction between the immune checkpoint receptor PD-1 principally expressed by T cells and its ligands PD-L1 and PD-L2, expressed on the surface of cancer cells and antigen-presenting cells, results in attenuated activation, proliferation and effector functions of T cells and other immune cells, hindering existent immune responses against aberrant cells.