PDCD1 and autoimmune disease: The PD-1/PD-L1 pathway is considered a particularly attractive therapeutic target in autoimmune diseases, because the development of PD-1 agonists could deliver the necessary ‘one-two punch’ to protect against self-reactivity: (I) augmenting iTreg function and (II) concomitantly suppressing the expansion and functions of activated effector T cells20.