The subject of this review is the humoral autoimmune response in Sjögren's syndrome.
Autoantibodies in this disease are primarily directed against the Ro/SS-A and La/SS-B
autoantigens and against
IgG (
rheumatoid factor). The Ro/SS-A and La/SS-B
autoantigens consist of a number of antigenic
proteins coupled to small
RNA molecules. These
RNA-
protein particles are present in all human cells and are strongly conserved throughout various species. Anti-Ro/SS-A and
anti-La/SS-B autoantibodies can be detected using counter-immunoelectrophoresis, immunoblotting technique, ELISA or
RNA precipitation assays. The preferred method of screening for anti-Ro/
SS-A antibodies in human sera is counter-immunoelectrophoresis;
anti-La/SS-B antibodies are best detected with the immunoblotting technique. Anti-Ro/
SS-A antibodies are found in 60% of patients with Sjögren's syndrome, but are not specific markers for this disease.
Anti-La/SS-B antibodies are present in approximately 40% of patients with Sjögren's syndrome; the only other disease where the antibody has been detected is
systemic lupus erythematosus (15% positive). The origin and possible pathogenetic role of
autoantibodies in Sjögren's syndrome is still unclear. Our view is that the current evidence supports a mechanism whereby
autoantibodies are the product of an oligoclonal B-cell proliferation. The only instance where
autoantibodies probably play a direct pathogenetic role is the occurrence of
congenital heart block in the offspring of anti-Ro/SS-A and anti-La/SS-B positive mothers.