Ro(SS-A) and anti-Ro(SS-A): an update

Anti-Ro/SSA antibodies are the antinuclear antibodies most commonly found in everyday clinical practice and are closely associated with Sjögren's syndrome, systemic lupus erythematosus and neonatal lupus. They play a pathogenic role in a variety of clinical manifestations, including skin lesions and neonatal lupus heart block. Autoantibodies to Ro(SS-A) recognize a ribonucleoprotein complex composed of small single-stranded RNAs (hYRNAs) and of one or more peptides. Four molecular forms of this complex have been differentiated based on the nature of the peptide: a lymphocyte and an erythrocyte Ro with a 60 kDa peptide, a lymphocyte Ro with a 52 kDa peptide and an erythrocyte Ro with a 54 kDa peptide. The Ro complex is found in most tissues and cells (erythrocytes, platelets), with differences in structure and quantity across tissues, species and embryonic development stages. Although its function remains unknown, its ability to bind nucleic acids and the fact that it shares homologies with gene regulation proteins suggest that it may participate in RNA transcription processes. A number of environmental factors (exposure to ultraviolet radiation, viral infections) may cause translocation of the Ro complex to nucleocytoplasmic and membrane sites where it is not normally found, thereby leading to the development of autoimmunity. The structure of the Ro(SS-A)-hYRNA complex and the development of autoimmunity are currently the focus of active research efforts that can be expected to improve our understanding of the clinical manifestations directly related to anti-Ro(SS-A) antibodies.