PDCD1 and Sepsis: The purpose of this review is to describe the underlying mechanisms of the immune deregulation in sepsis, to summarize the failed history of clinical trials testing therapeutic agents for host immune responses in sepsis, and to specifically address treatments aimed to reverse the immunosuppression, focusing in particular on the programmed cell death protein 1/programmed death ligand (PD-1/PD-L) pathway on T cells.