Figure 1.

Deactivated T Cell (Left): when programmed-death receptor (PD-1) on the T cell binds to programmed death-ligand 1 (PD-L1) on the tumor cell, the T cell becomes deactivated, allowing the cancer cell to evade immune attack. Inhibitors of PD-1 and PD-L1 can prevent the tumor cell from binding to PD-1, enabling the T cell to remain active and co-ordinate an attack (on the Right). Reproduced with permission of Terese Winslow LLC. Credit: For the National Cancer Institute © 2015 Terese Winslow LLC, U.S. Govt. has certain rights.