Both extrinsic and intrinsic pathways contribute to decreased lymphocyte apoptosis in vivo. Mice underwent sham procedure, CLP, CLP plus anti-PD-L1 antibody administration, or CLP plus isotype administration. Thymus was harvested 24 h after surgery and stained for annexin V and propidium iodide (PI) (A, D) or FITC-labeled IEHD-FMK (B, E) or LEHD-FMK (C, F) which can irreversibly binds to activated caspase-8 or activated caspase-9. (D), (E), and (F) are the representative flow cytometry dot plots. Values in the upper right quadrant indicate the percent of apoptotic cells, caspase-8 or caspase-9 positive cells, respectively. * P <0.05.