1% sodium azide, and then stained with the amine-reactive LIVE/DEAD fixable violet dead cell

stain kit (Molecular Probes, Invitrogen) 47 and with allophycocyanin (APC)-conjugated anti-CD4+ mAb (BD Pharmingen, San Josè, CA, USA) in incubation buffer (PBS-1% FCS-0.1% Na azide) for 30 min at 4°C. Subsequently, PBMC were washed, permeabilized (Cytofix/Cytoperm Kit, BD Pharmingen) according to the manufacturer’s instructions and stained for intracellular cytokines with anti-IFN-γ-PE, anti-IL-2-FITC Y27632 and TNF-α-PECy7, or isotype-matched control mAb. All mAb were from BD Pharmingen. Cells were washed, fixed in 1% paraformaldehyde and at least 250 000 lymphocytes were acquired using a modified FACS Aria (BD Biosciences), following gating according to forward and side scatter plots. FACS plots were analysed using FlowJo software (version 6.1.1; Tree Star, Ashland, OR, USA). Nonviable cells were excluded using a dump channel versus CD4+. Percent frequencies of the different combinations of IFN-γ, IL-2 and TNF-α-positive cells following antigenic stimulation were calculated within the total population of CD4+ T cells and background values subtracted (as determined from the medium alone control). Nonspecific background was extremely low when more GSK2126458 than one cytokine was examined. A cutoff of 0.01% was used as described previously

48; values below this were set to zero. PBMC were stimulated in IMDM (Invitrogen, Breda, The Netherlands) containing 10% pooled human serum and ESAT-6+CFP-10 peptides, tested in pools containing 1 μg/mL per peptide. Cells were cultured in a humidified incubator at 37°C with 5% CO2 for 6 days, the last 18 h in the presence of 5 μg/mL Brefeldin A (Sigma, Zwijndrecht, The Netherlands). Intracellular staining was performed using intrastain reagents (Dako cytomation, Heverlee,

Belgium). Ab used were CD3−APC-Cy7, CD4+-PE-Cy7, CD8+-Am Cyan, IFN-γ-Alexa 700, IL-2-PE and TNF-α-APC (all from BD Biosciences, Alphen aan den Rijn, The Netherlands). Data were acquired on a BD LSRII flow cytometer using FACSDiva software (BD Biosciences) and analysed using FlowJo software (Tree Star). Graphical representations were made using Pestle and Spice software, software provided free of charge by the National Institute of stiripentol Allergy & Infectious Disease (Bethesda, MD, USA), written in collaboration with Dr. Mario Roederer, Senior Investigator of the ImmunoTechnology section of the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases. Median and interquartile range of data were calculated and Mann–Whitney U-test was used to compare medians. Chi-square testing was used for dichotomous (positive/negative) measures. Values of p<0.05 were considered significant. Data were analyzed using statistical software SYSTAT 11 (Systat Software) or Graph Pad Prism (4.02) (Graph Pad Software). The authors acknowledge Dr.