In trauma patients, PD-1-related molecule expressions on monocytes were significantly increased in comparison with healthy individuals (for PD-1: control value: 5.0% versus 9.6%, P = 0.005; for PD-L1: control value: 10.2% versus 40.1%, P < 0.001; and for PD-L2: control value: 2.6% versus 7.2%, P < 0.001). Here, PDCD1 is linked to injury.