Association of Anti–Acidic Ribosomal Protein P0 and Anti–Galectin 3 Antibodies With the Development of Skin Lesions in Systemic Lupus Erythematosus

Abstract

The specific autoantibodies and antigens that mediate systemic lupus erythematosus (SLE)-related organ injuries remain largely unknown. This study was undertaken to investigate the antibody-mediated immune response that leads to SLE skin lesions. The study included 85 SLE patients with lupus-specific skin lesions and 31 without skin lesions. The reactivity of serum antibody with skin antigens was determined by immunoblotting using human foreskin as the substrate. Skin antigens were identified using mass spectrometry. Serum antibody was isolated by affinity purification and was injected intracutaneously into mouse skin to determine pathogenicity. Serum antibody levels were monitored by enzyme-linked immunosorbent assay. We determined that 78% of the patients with skin lesions had serum antibodies reactive with 35-kd and/or 25-kd skin antigens, which was significantly higher than the percentage of patients without skin lesions (P < 0.0001), suggesting a correlation between immune response and skin lesions. Acidic ribosomal protein P0 (RPLP0) and galectin 3 were 2 target antigens identified from 35-kd and 25-kd proteins, respectively. Purified serum anti-RPLP0 and anti-galectin 3 antibodies induced lupus-like histologic changes after intracutaneous injection. Anti-RPLP0 and anti-galectin 3 antibody levels were significantly higher in SLE patients than in healthy controls and decreased with skin recovery. Anti-galectin 3 antibody levels were not significantly higher in SLE patients than in patients with dermatomyositis or scleroderma, but strongly related to lupus cutaneous vasculitis. Additionally, levels of the 2 antibodies were positively correlated with leukopenia and C3 deficiency, and the anti-RPLP0 antibody level was also positively correlated with arthritis and SLE disease activity. Our findings indicate that the immune response mediated by serum anti-RPLP0 and anti-galectin 3 antibodies plays a key role in the pathogenesis of SLE skin lesions. These findings provide new insights into the mechanism of SLE-related organ disorders.