In separate experiments, whole blood was treated with 10 μg/mL brefeldin A (Invitrogen, Carlsbad, CA, USA) for 60 min at 37°C in 5% CO2 followed by incubation in the dark for 15 min at room temperature with anti-CD4 FITC, anti-CD14 FITC (Beckman Coulter) and anti-CD45 PC5 followed by red blood cells lysis. Stained cells were then washed with Dulbecco’s Phosphate Buffered Saline and permeabilized with the IntraPrep Parmeabilization Reagent kit (Beckman Coulter). Anti-IL-6 PE (Beckman Coulter) was added and analyzed after flow cytometry.