ELISPOT
ELISPOT was carried out with ELISpotPLUS Human IgM Kit (MABTECH AB, Sweden). In brief, 104 purified CD27+IgD+ B cells and other B cell types from SLE and HC patients, respectively, were assessed for IgM after incubation with anti-CD40 (3µg/ml, eBioscience) and CpG (10µg/ml, Invivogen, USA) for 24h. An ImmunoSpot Analyzer (Cellular Technology Ltd., USA) was utilized for data analysis.