SS-B Antibody Test

The SS-B antibody targets a protein called La (also known as SS-B), which plays a critical role in the health and maintenance of RNA inside your cells. RNA (ribonucleic acid) acts like a messenger, carrying instructions from your DNA to the parts of the cell that make proteins. Specifically, the La protein helps stabilize and properly process certain small RNA molecules, especially those made by a type of enzyme called RNA polymerase III. This stabilization process is essential because it protects immature RNAs from being degraded too early and ensures they are properly matured for their important cellular roles.

In autoimmune conditions, however, the immune system mistakenly produces antibodies against the La protein. These autoantibodies are called anti-SS-B antibodies. Their presence is most commonly associated with two autoimmune diseases: Sjögren’s syndrome (SS) and systemic lupus erythematosus (SLE). When detected alongside anti-SSA (Ro) antibodies, anti-SS-B antibodies provide strong evidence for these diagnoses.

When anti-SS-B antibodies are found together with anti-SSA antibodies, they significantly strengthen the suspicion of autoimmune diseases like Sjögren’s syndrome and lupus. However, when anti-SS-B antibodies are detected alone—without anti-SSA—they are much less meaningful. Studies show that isolated anti-SS-B positivity does not reliably correlate with autoimmune diseases and often does not add diagnostic or prognostic value. In fact, people with only anti-SS-B antibodies often have clinical features similar to healthy individuals.

Anti-SS-B antibodies can sometimes be found at very low levels in healthy people, though at much lower concentrations and binding strengths compared to those with autoimmune disease.