Figure 2: PD-L1 signaling blockade decreased CD8+ T cell death in vitro but did not have an effect on T cell proliferation in response to A(H1N1)pdm09 virus. PBMCs from healthy individuals were stimulated with A(H1N1)pdm09 for 18 h, washed, labeled with CFSE, and treated on days 0, 3, and 5 with a blocking anti-PD-L1 antibody or an isotype control. Cells were incubated for 7 days, and T cell proliferation and cell death were determined. SEB was used as a control. (a) Representative histograms of the CD4+ T cell CFSE dilution from one individual. (b, c) T cell proliferation expressed as the percentage of CFSE+ dividing cells. (d) Representative plot of Annexin V and 7-AAD staining to evaluate CD8+ T cell apoptosis, which was gated from CD2+ and CD8+ cells. (e, f) Percentage of early apoptotic (Annexin V+ 7-AAD-) T cells. ( , error bars indicate SEM). * by Student’s -test.