Background information
Ro autoantigens are of clinical significance because directed against them are found in most patients with primary Sjqgren syndrome, subacute cutaneous lupus erythematosus (SLE), neonatal lupus erythematosus, ANA-negative lupus erythematosus, and systemic lupus erythematosus-like disease secondary to homozygous C2 or C4 complement deficiency (1). Ro/SSA is a ribonucleoprotein that binds to auto in 35 to 50% of patients with SLE and in up to 97% of patients with Sjqgren syndrome (2). The Ro/SSA particle consists of a single immunoreactive protein noncovalently bound with one of four small RNA molecules (2). Most anti-Ro/SSA-positive sera detect not only the main protein, but also a smaller Ro/SSA protein (2). The genes which encode the smaller and larger proteins map to human chromosomes 11p15.5 and 1q31, respectively (3?). La/SSB is an autoimmune RNA-binding protein that plays a role in the transcription of RNA polymerase III was originally defined by its reactivity with auto from patients with Sjé°ƒren syndrome and SLE (6).
