High prevalence of autoantibodies against the nuclear High Mobility Group (HMG) protein SSRP1 in sera from patients with systemic lupus erythematosus, but not other rheumatic diseases

Objective. To evaluate the presence of autoantibodies to the high mobility group (HMG) structure specific recognition protein 1 (SSRP1) in sera from patients with systemic lupus erythematosus (SLE) or other rheumatic diseases. Methods. Antibodies to SSRP1(anti-SSRP1) were measured in sera from patients with SLE, Sjögren's syndrome (SS), ulcerative colitis (UC), systemic sclerosis (SSc), rheumatoid arthritis (RA), and sera from healthy individuals by both an enzyme-linked immunoassay (ELISA) and Western blotting (WB) using the recombinant SSRPI N-terminus as antigen. Results. We found 28.8% of the sera from patients with SLE contained anti-SSRP1 by both ELISA and WB assay, compared to 8.3% of the sera from healthy individuals. When the 40 sera from patients with other autoimmune diseases were tested, only 2 sera (5%) from individuals with SS showed a moderate reactivity to SSRP1 in both ELISA and WB assays. Conclusion. The results show that anti-SSRP can be identified in sera from patients with SLE, but not with other rheumatic diseases and may thus help the diagnosis of SLE in the presence of appropriate clinical findings.