THE MOLECULAR BASIS OF THE SSA/Ro ANTIGENS AND THE CLINICAL SIGNIFICANCE OF THEIR AUTOANTIBODIES

The SSA/Ro antigens are nuclear and cytoplasmic polypeptideswhich serve as autoantigens in systemic lupus erythemato-sus(SLE) and Sjögren's syndrome (SS). They contain two majorisoforms of 60 and 52 kD. The former is the native antigen whilethe latter is a major autoantigen in its denatured form. A thirdprotein of 46 kD termed ‘calreticulin-Ro’ is anautoantigen found in the sera of some patients with SLE. However,it is probably unrelated to the SSA/Ro system. The clinicalrelevance of anti SSA/Ro antibodies in rheumatic diseases hasalso been considered. Initially these antibodies were thoughtto be an epiphenomenon of autoimmune diseases. Recent studieshave shown that they are associated with specific clinical manifestationsand disease subsets. Furthermore, animal models have demonstratedthat they may enhance tissue damage. It seems that anti-SSA/Roantibodies may play a role in the pathogenicity of SLE and SS. KEY WORDS: SSA/Ro antigen, Autoantibodies, Systemic lupus erythematosus, Sjögren's syndrome