antiLaSSB

Anti-La/SSB antibodies, often called anti-La or anti-SSB, are autoantibodies directed against the La/SSB ribonucleoprotein complex, a cellular RNA-binding protein involved in RNA processing. The La antigen (SS-B) is a 48-kDa protein that associates with various RNA transcripts and is found in the nucleus and cytoplasm of many cell types. In autoimmune conditions, B cells produce anti-La/SSB antibodies, frequently alongside anti-Ro/SSA antibodies. The presence of anti-La/SSB is a useful serologic marker in the diagnostic workup for connective tissue diseases.

Clinical associations are strongest with Sjögren's syndrome, where anti-La/SSB antibodies occur in a substantial subset of patients and commonly accompany anti-Ro/SSA antibodies. They are also seen in systemic lupus erythematosus and other autoimmune diseases. A notable relevance is the risk of neonatal lupus and congenital heart block when pregnant individuals carry anti-SSA/SSSB antibodies, including anti-La/SSB, which can cross the placenta and affect the fetus.

Detection and interpretation rely on laboratory assays such as ELISA, immunoblot, and line immunoassays, often performed as part of a broader autoantibody panel. Indirect immunofluorescence on HEp-2 cells is not specific for La/SSB and positive confirmation typically requires antigen-specific testing. Interpretation of results should consider the clinical context and the presence of other autoantibodies, particularly anti-Ro/SSA.

In classification and prognosis, anti-La/SSB positivity supports a Sjögren's syndrome diagnosis when combined with other criteria and may correlate with particular disease features, though absence of anti-La/SSB does not exclude the disease. Prevalence and associations can vary by population and disease.