HAVCR2 and Sepsis: In addition to the PD-1/PD-L1 recognition system, other immune checkpoints, such as cytotoxic T lymphocyte antigen-4 (CTLA-4), T cell membrane protein-3 (TIM-3), lymphocyte activation-gene-3 (LAG-3) and 2B4, are upregulated during the course of sepsis 150.