Abstract: Objective To develop a new serodiagnostic method for systemic lupus erythematosus(SLE) using a dot inununogold filtration assay(DIGFA). Methods The 42-kD egg nuclear protein, which was proved to specifically react with autoantibodies in the sera of many patients with SLE in our previous study, was separated from the chicken eggs by SDS-PAGE and analyzed by Dot-ELISA. A dot immunogold filtration assay using 42-kD nuclear protein of chicken egg as antigen was developed. Sera from patients with SLE before and after treatment(n=191),dennatomyositis or polymyositis(DM/PM)(n=72),progressive systemic sclerosis(PSS)(n=48),mixed connective disease(MCTD)(n=78),and healthy control subjects(n=100)were assayed by the established DIGFA. The primary evaluation parameter was the geometric mean reciprocal titer(GMRT)of specific IgM and IgG. Results The sensitivity and specificity of the established DIGFA were 94.24%(180 of 191 SLE sera showed a positive result)and 100.00%(all sera of healthy controls, patients with DM/PM, PSS, and MCTD showed a negative result), respectively. Of the 174 SLE patients with both specific anti-42-kD nuclear protein 1gM and IgG antibody in the sera, 71 were with active SLE and 103 were with inactive SLE. In those with active SLE, the specific IgM and IgG in sera before treatment showed significant higher GMRT than after treatment(768.84士26.43 vs 367.53±18.52, 629.25±30.05 vs 405.72±16.35, respectively)(P<0.01).Meanwhile, in those with inactive SLE, the GMRT of specific IgM and IgG was also significantly reduced after treatment (421.34±23.12 to 295.63±20.57, 452.67±16.35 to 358.73±21.27, respectively)(P<0.01). Conclusions The results suggest that DIGFA using 42-kD nuclear protein of chicken egg as antigen is a valuable tool for the setodiagnosis of systemic lupus erythematosus, and GMRT of anti-42 kD nuclear protein-specific IgM determined by DIGFA is superior as an efficacy parameter to those of specific IgG.

Key words: Lupus erythematosus, systemic, Dot immunogold filtration assay, 42 000 nuclear protein of chicken egg, Serodiagnosis