Anti-topoisomerase I (anti-Scl-70) antibodies in patients with systemic lupus erythematosus.

OBJECTIVE

To investigate the presence and clinical significance of anti-Scl-70 antibodies in patients with systemic lupus erythematosus (SLE).

METHODS

Levels of antibodies against Scl-70 were determined by a commercial clinical enzyme-linked immunosorbent assay (ELISA) during routine evaluation. Results were verified by an additional ELISA with a characterized bovine Scl-70, by ELISA with a recombinant human topoisomerase I, by Western blot, and by double diffusion in agar gel. Disease activity was estimated retrospectively by the Systemic Lupus Activity Measure (SLAM).

RESULTS

Of 128 consecutive SLE patients, 25% were positive for anti-Scl-70 antibody; this antibody activity was cognate in nature. No SLE patient could be classified as also having systemic sclerosis. The levels of anti-Scl-70 were significantly correlated with the SLAM score for the entire cohort (r = 0.563, P < 0.001) and for 7 individual patients with multiple longitudinal measurements (r = 0.755-0.951, P < 0.001; n = 6) (r = 0.378, P < 0.05; n = 1). A significant correlation was also found between the levels of anti-Scl-70 and anti-double-stranded DNA antibodies (r = 0.558, P < 0.001). Patients with anti-Scl-70 had significantly higher risk of pulmonary hypertension (P < 0.01) and renal involvement (P < 0.001) than patients without this antibody.

CONCLUSION

Anti-Scl-70 antibody is present in a significant subset of patients with SLE. For this subset, it offers a good correlate of disease activity and suggests increased risk for pulmonary hypertension and nephritis.