Blood sera of patients with autoimmune diseases scleroderma (Scl), systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA) have been shown to yield a specific immune response to topoisomerase I, the product of expression of a cDNA fragment cloned into λgt11 and monoclonal antibodies (MAB) to the enzyme. The ‘topoisomerase test’ is not absolutely specific for Scl. The stable positive response of autoimmune sera to anti-topoisomerase monoclonal antibodies has a specific character and is associated with the interaction of the Fab fragment of MAB with the IgG fraction of autoimmune serum. The response observed indicates the induction of anti-idiotypic antibodies against topoisomerase. The anti-idiotype, isolated by HPLC and affinity chromatography demonstrated the following functional activities: (i) the immunological reaction against DNA; (ii) high-affinity DNA-binding with topoisomerase-specific consensus; (iii) ability to compete with the native enzyme for binding with DNA and MAB to topoisomerase; (iv) immunological reaction against MAB to topoisomerase.
