The concentration of CXCL13 in serum was measured using human CXCL13/BLC/BCA-1 ELISA kits (CUSABIO, Wuhan, China) according to the  manufacturer’s instructions and as our previous studies[15].We also detected the serum level of total IgG ANA  and concentration of anti-dsDNA applying enzyme-linked immunosorbent assay (ELISA) according to the manufacturer’s protocol and our previous studies[16]. The avidity of IgG ANAs by ELISA and indirect immunofluorescence (IIF) assay were processed as in the standard test. The relative avidity index (RAI) was used to evaluate the avidity of IgG ANAs. The serum levels of C3 and C4 were determined by nephelometry with the Image Immunochemistry System (Roche Cobas 8000, Germany).