Ex vivo cell assay.
PBMCs were resuscitated and cultured in RPMI-1640 medium (Sigma-Aldrich) with 10% FBS, 100 U/mL penicillin, and 0.1 mg/mL streptomycin. For PD-L1 treatment, 96-well round-bottom plates were precoated with human IgG1 Fc (10 μg/mL, R&D Systems, 110-HG-100) as the control or human PD-L1 Fc Chimera Protein (10 μg/mL, R&D Systems, 156-B7-100) overnight at 4°C. The cells were seeded in duplicate plates at a density of 1 × 10