AntiLa

Anti-La antibodies, also known as anti-La/SSB antibodies, are autoantibodies directed against the La antigen, a 47- to 50-kilodalton RNA-binding protein encoded by the SSB gene. The La antigen participates in RNA processing and maturation, including binding and protecting RNA polymerase III transcripts such as pre-tRNA, and resides predominantly in the nucleus with some cytoplasmic localization.

In clinical practice, anti-La antibodies are a feature of autoimmune rheumatic diseases, most notably Sjögren's syndrome, where they occur alone or together with anti-Ro/SSA antibodies. They are also detected in systemic lupus erythematosus and less commonly in other autoimmune conditions. The combined presence of anti-La and anti-Ro antibodies increases diagnostic specificity for certain autoimmune syndromes, and their occurrence can correlate with various disease features. Anti-La antibodies may also appear in healthy individuals with autoimmune tendencies, though this is less common.

Testing and interpretation: Anti-La antibodies are detected by serologic assays such as ELISA, immunodiffusion, immunoblotting, or line immunoassays. Results are interpreted in the context of clinical symptoms and other autoantibody tests, particularly anti-Ro/SSA. The absence of anti-La does not exclude Sjögren's syndrome or SLE.

Neonatal considerations: Maternal anti-La antibodies can cross the placenta and, with anti-Ro/SSA antibodies, are associated with neonatal lupus syndrome, which can include congenital heart block, skin rash, and liver abnormalities. Management during pregnancy focuses on monitoring and treating the underlying maternal autoimmune disease.