The SL/Ki system in connective tissue diseases: incidence and clinical associations.

In a clinical and serological study carried out on 516 subjects with different connective tissue diseases, anti-SL/Ki autoantibodies were found in 12% of patients with systemic lupus erythematosus, 14% of patients with mixed connective tissue disease, 18% of patients with different kinds of vasculitides, and 3% of patients with Sjögren's syndrome. In SLE patients, no significant clinical association was found with the SL/Ki system, but the incidence of the antibody was nearly three-fold higher in males than in females. Most sera contained other autoantibodies; a statistically significant serological association has been found between SL/Ki and PCNA antibodies (p less than 0.05).