Antibodies to the Ro/SS-A antigen are classically described in association with autoimmune diseases such as systemic lupus, and Sjögren's syndrome. More recently, two different target proteins have been differentiated: Ro60 (60 kDa) and Ro52 (52 kDa), which have distinct biochemical and immunological functions. Indeed, Ro52 corresponds to TRIM21, belonging to the Tripartite Motif Protein (TRIM) family. It is implicated in protein ubiquitination, pro-inflammatory states (interleukin 2), and apoptosis mechanisms. Ro60 antigen is a protein component of small cytoplasmic ribonucleoprotein complexes (hY-RNA complexes) which can bind misfolded, non-coding RNA, probably taking part in their final degradation. It also seems to have an important function in cell survival after ultraviolet irradiation.
Clinically, it has been suggested that different associations of anti-Ro60 (Ro60 Ab) or anti-Ro52 antibodies (Ro52 Ab) in patients may associate with different phenotypes such as systemic lupus erythematosus, neonatal lupus, and fetal atrioventricular blockade, primary Sjögren's syndrome, or inflammatory myositis. However, some authors question the diagnostic utility of individual detection of Ro52 and Ro60 antibodies as their association in certain studies concerning the Ro/SS-A system is contradictory.
Just like anti-Ro60, anti-Ro52 is commonly found in patients with SLE and Sjogren's syndrome, and occasionally in other autoimmune disorders. Anti-Ro52 autoantibodies are also found in patients with systemic sclerosis, polymyositis, and dermatomyositis. Anti-Ro52 are often found in patients with interstitial lung involvement. Studies show that 10-45% of myositis patients are positive for Ro52 antibodies.
