Isolation of peripheral blood mononuclear cells (PBMCs)
Heparinized peripheral blood (approximately 3 mL) was obtained from patients and healthy children. Sample blood was diluted with an equal volume of phosphate-buffered saline (PBS). Mononuclear cells were separated by centrifugation using Lymphprep®, aliquoted in Cellbanker®, and subsequently stored in a −80°C refrigerator until analysis. All patients and control subjects were free from any infectious episodes at the time of venipuncture.