PDCD1 and cancer: The panel of dual blocking, single blocking, and non-blocking mAbs developed here will allow us to explore the functional roles of PD-1, PD-L1, and PD-L2 in devils and may help to shed light on immune evasion by cancers and the role of PD-1 and PD-L1 in allograft rejection that is relevant to humans and other species.