Figure 1: PD-L1 is expressed on human dendritic cells and T cells, whereas PD-1 is expressed only on T cells after exposure to A(H1N1)pdm09 virus. PBMCs were stimulated with A(H1N1)pdm09 virus (pH1N1), seasonal influenza virus (H3N2), staphylococcal enterotoxin B (SEB), or synthetic TLR7 agonist (CL264); PD-L1 and PD-1 expression on DCs and T cells was analyzed by flow cytometry. (a) Fold increase in PD-L1 expression on conventional (cDCs) and plasmacytoid dendritic cells (pDCs), CD4+, and CD8+ T cells after 18 h of stimulus. M: medium. (b) PBMCs were stimulated with live or UV-inactivated pH1N1 for 18 h; virus and PD-L1 expression was measured on cDCs and pDCs. (c) Kinetics of PD-L1 and PD-1 expression on CD4+ and CD8+ T cells induced by pH1N1 or SEB. PBMCs were stimulated with pH1N1 for 2 h, then cycloheximide (CHX) was added for another 16 h, and PD-L1 expression on CD4+(d), CD8+ T cells (e), pDCs (f), and cDCs (g) was measured by flow cytometry. ( donors, error bars indicate standard error of the mean (SEM)). *, **, and *** by one way ANOVA test with Bonferroni posttest.