B-cell epitopes of the intracellular autoantigens Ro/SSA and La/SSB: tools to study the regulation of the autoimmune response.

A common serologic finding in systemic autoimmune diseases is the presence of autoantibodies against intracellular autoantigens. Although their pathogenesis is not fully understood, autoantibodies are important tools for establishing diagnosis, classification and prognosis of autoimmune diseases. In Systemic Lupus Erythematosus (SLE) and Sjögren's syndrome (SS) autoantibodies mainly target multicomponent ribonucleoprotein complex Ro/La RNP. The last years, the main characteristics, the clinical significance of the anti-Ro/SSA and anti-La/SSB autoantibodies, their biologic function, as well as their B-cell antigenic determinants (epitopes) have been addressed. More specifically, the structural characteristics and clinical associations of epitopes along with their utility as tools to investigate the autoimmune response have been investigated in detail. New insights for the pathogenetic role of epitopes in initiation, propagation and regulation of systemic autoimmunity have been emerged. In this regard, the role of epitope spreading in the diversification of autoimmune response and the anti-idiotypic antibodies in the regulation of autoantibodies (idiotypic) response are addressed.