PDCD1 and Sepsis: An important feature of immunosuppression is T cell exhaustion, which was recently recognized following many trials for sepsis involving immunoregulatory therapies, such as PD-1 blockade, interleukin 7 administration, interleukin 15 administration, IFN-γ administration, and CTLA-4 blockade (2, 21, 31, 33).