Septic patients, especially those with severe sepsis and septic shock, had significantly higher PD-1 expression levels on CD4+ or CD8+ T cells, PD-L1 expression on monocytes, sPD-1, and sPD-L1 levels compared to patients with non-septic infections, non-infectious inflammation, and a healthy control group. This evidence concerns the gene PDCD1 and infectious disease.