Cell sorting and culture
Fluorescence-activated cell sorting (FACS) was utilized to purify CD27+IgD+ B cells. Briefly, 10-ml blood specimens were obtained from SLE and HC patients, followed by peripheral blood mononuclear cell (PBMC) isolation by Ficoll density-gradient centrifugation and staining as described above. Next, the target cells were collected in RPMI 1640 containing 10% FBS and 2% antibiotics on a FACS Aria II flow cytometer as directed by the manufacturer (95–99% purity).