Fig. 3. CHECKPOINT INHIBITORS & ANTI-TUMOR IMMUNE RESPONSE: Inhibitors such as anti-PD1 bind to and neutralize T-cell-bound inhibitory receptors such as PD-1. Others like anti-PD-L1 bind to and neutralize inhibitory ligands such as PD-L1, which are overexpressed on tumor cells. This binding suppresses inhibitory signals. As a result, inflammatory signals are enhanced. The tumor undergoes immune attack and is eliminated. Autoimmune side effects are also possible.