Background of the antigen
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).
