2.2. Specimen Collection and Pretreatment

Fresh PB samples were collected from all participants in sodium heparin tubes, whereas fresh 10–20 mL PF samples were collected in parallel from those participants belonging to cohort 2. The white blood cell count in the PF was adjusted to 2–10 × 10⁶ cells/mL before analysis. Subsequently, PB and PF samples were split into three tubes (1 mL each tube): a negative control tube containing RPMI-1640 medium only, a test tube containing 5 μg/mL ESAT-6 and CFP-10 (Wantai, Beijing, China), and a positive control tube containing 10 μg/mL phytohemagglutinin (PHA). All cells were simultaneously costimulated with 1 μg/mL anti-CD28 and anti-CD49d antibodies (BD Biosciences). The tubes were then incubated at 37 °C in 5% CO₂ for 24 hr.