IgG from patients with systemic sclerosis bind to DNA antitopoisomerase 1 in normal human fibroblasts extracts

By using a semi-quantitative immunoblotting technique, we have analyzed serum immunoglobulin G (IgG) reactivities of patients with limited cutaneous systemic sclerosis and anticentromere antibodies, patients with diffuse systemic sclerosis and antitopoisomerase 1 antibodies, patients with diffuse systemic sclerosis without antitopoisomerase 1 or anticentromere antibodies and age- and gender-matched healthy controls with normal human skin fibroblasts and HEp-2 cells antigens. Serum IgG reactivities of patients with diffuse systemic sclerosis and antitopoisomerase 1 antibodies differed significantly from those of healthy controls or systemic sclerosis patients in other groups for reactivity with fibroblast proteins. IgG from patients with antitopoisomerase 1 antibodies bound to a 90 kDa fibroblast band and to a 100 kDa protein band in a HEp-2 cell protein extract. These two bands were further identified as DNA topoisomerase 1. Our results indicate that IgG from patients with diffuse systemic sclerosis bind DNA topoisomerase 1 in normal human fibroblasts extracts.