Antibodies to SS-B in chronic inflammatory connective tissue diseases. Relationship with HLA-Dw2 and HLA-Dw3 antigens in primary Sjögren's syndrome.

SS-B antigen, purified from rabbit thymus, was used in an indirect enzyme immunoassay to demonstrate the presence of IgG-, IgA-, and IgM-type SS-B antibodies in sera from patients with well-defined and characterized chronic inflammatory connective tissue disease. High levels of antibodies to SS-B were found in patients with primary and secondary Sjögren's syndrome. Patients with Sjögren's syndrome secondary to systemic lupus erythematosus had significantly higher SS-B antibody values than patients with Sjögren's syndrome secondary to rheumatoid arthritis or patients with rheumatoid arthritis or systemic lupus erythematosus, alone. Two patients with rheumatoid arthritis without secondary Sjögren's syndrome also had a markedly elevated level of antibodies to SS-B. Antibodies of all immunoglobulin classes were found, although the highest values were either IgG- or IgM-type. In primary Sjögren's syndrome, antibody values to SS-B were higher in patients with HLA-Dw2 and/or HLA Dw3 than in those with other HLA-Dw types. We conclude that these antigens or specific immune-response genes close to the D region may be important for the development of antibodies to SS-B.