Figure 1

PD-1, PD-L1 and HLA-DR expression in septic and non-septic patients. Septic and non-septic patients were identified and heparinized blood samples obtained at a maximum of four time points during their septic course. Peripheral blood mononuclear cells were stained for lymphocyte (CD4, CD8) and monocyte markers (CD14). Immunostaining was also performed for programmed cell death 1 (PD-1), programmed cell death ligand 1 (PD-L1) and human leukocyte antigen-DR (HLA-DR). Flow cytometry revealed an increase in PD-1 and PD-L1 expression in CD8 T cells and monocytes from septic versus non-septic patients. HLA-DR expression was decreased in monocytes from septic versus non-septic patients as well. Data are from 43 septic (70 data points) and 16 non-septic patients (16 data points). Septic and non-septic patients had up to four serial blood samples obtained depending upon the duration of their illness and/or discharge from the ICU; - first draw = days 1 to 3 after admission to the ICU, days 4 to 7 (second blood draw), days 8 to 12 (third blood draw), and days 13 to 21 (fourth blood draw) after sepsis onset. Most non-septic patients were discharged from the ICU within four to five days and, therefore, they had less serial blood samples obtained compared to septic patients.