Human B cell isolation and cultures
Venous peripheral blood was withdrawn from each patient and healthy control subject. B cells were isolated by positive selection using CD19 beads, according to the manufacturer’s instructions (Miltenyi, Bergisch Gladbach, Germany; routine purity > 95%). Cell culture was performed in human B cell culture medium (Lonza, Walkersville, MD, USA) supplemented with 10% foetal bovine serum (FBS) and 1% penicillin/streptomycin.