PDCD1 and Sepsis: In addition to increased PD-1 and Tim-3 expression, several studies involving sepsis mice and patients have also reported increases in the expression of other coinhibitory receptors such as TNF-related apoptosis-inducing ligand (TRAIL), B and T lymphocyte attenuator (BTLA), and lymphocyte activation gene-3 (LAG-3) in T cells (24, 61).