Peripheral blood mononuclear cells
Peripheral blood mononuclear cells (PBMC) were isolated from fasting blood collected in sodium citrate Vacutainer Cell Preparation Tubes (Becton Dickinson, NJ). Cells were resuspended in cell culture medium (RPMI-1640, 10% fetal bovine serum, 100 U penicillin, 100 µg streptomycin) and plated in 12-well plates at the density of 2 × 10