The molecular basis of the SSA/Ro antigens and the clinical significance of their autoantibodies.

The SSA/Ro antigens are nuclear and cytoplasmic polypeptides which serve as autoantigens in systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS). They contain two major isoforms of 60 and 52 kD. The former is the native antigen while the latter is a major autoantigen in its denatured form. A third protein of 46 kD termed 'calreticulin-Ro' is an autoantigen found in the sera of some patients with SLE. However, it is probably unrelated to the SSA/Ro system. The clinical relevance of anti SSA/Ro antibodies in rheumatic diseases has also been considered. Initially these antibodies were thought to be an epiphenomenon of autoimmune diseases. Recent studies have shown that they are associated with specific clinical manifestations and disease subsets. Furthermore, animal models have demonstrated that they may enhance tissue damage. It seems that anti-SSA/Ro antibodies may play a role in the pathogenicity of SLE and SS.