“…Whole blood from a patient with systemic lupus erythematosus (SLE) was diluted with PBS at room temperature, and subjected to density gradient centrifugation over Ficoll (GE Healthcare, Uppsala, Sweden) to isolate PBMC. Active SLE patients exhibit significant B lymphopenia, with increased frequencies and absolute numbers of PB/PC in peripheral blood . PBMC were washed with PBS/0.2% BSA, and stained at 4°C for 15 min with a cocktail of the following mAbs: CD19 (clone SJ25C1, BD), CD27 (clone 2E4; Sanquine), CD20 (L27, BD), CD14 (M5E2, BD), CD3 (UCHT1, BD), CD38 (HIT2, BD), CD138 (B‐B4, Miltenyi Biotec).…”