Use of molecular cloning methods to map the distribution of epitopes on topoisomerase I (Scl-70) recognized by sera of scleroderma patients.
 We report the initial molecular characterization of the autoimmune response against DNA topoisomerase I (topo I; Scl-70).
 Sera from 36 patients with scleroderma and 4 healthy control subjects were studied using 6 subcloned portions of topo I.
 Twenty-three sera recognized at least 2 independent epitopes on the molecule.
 Therefore, anti-topo I, like other non-organ-specific autoantibodies characterized to date, is polyclonal and multifocal.
 The cloned protein should prove suitable for sensitive early detection of anti-topo I in the clinical setting.
