Flow cytometry analysis
For CD27+IgD+ B cell detection, 2-ml blood specimens were collected from SLE and HC patients, and 100µl fresh whole blood cells was extracted and incubated with the following antibodies:APC-CY7-labeled anti-CD19 (BioLegend, USA), APC-linked anti-CD27 (eBioscience, USA) and FITC-labeled anti-IgD (eBioscience). Then, erythrocyte lysis was carried out with the RBC lysis buffer (MultiSciences, China) and the remaining cells were assessed on a FACS Aria II. Dead cells were excluded based on scatter properties and 7-AAD staining.