Scl-70 Antigen

The Scl-70 antigen is an abundant nuclear protein susceptible to proteolysis (2). It has been shown that the Scl-70 antigen can be obtained as an extractable immunoreactive fragment (70 kD) of a larger protein (100-105kD), which has been shown to be Topoisomerase I (3). Anti-Scl-70 antibodies were originally described as precipitating autoantibodies in sera of patients with a connective tissue disease. It was later realized that some patients with diffuse scleroderma characteristically have a high incidence of this autoantibody (1). The presence of autoantibodies against the Scl-70 antigen has been reported to have prognostic value in the diagnosis of diffuse scleroderma, also termed Progressive Systemic Sclerosis (1). It has also been reported that autoantibodies to Scl-70 are a specific serologic marker for Systemic Sclerosis (3), and present in high proportions of Acrosclerosis (4). Anti-Scl-70 is not usually present in other autoimmune rheumatic diseases unless some cutaneous symp