SS-B/La antigen purification, and ELISA detection of anti-SS-B/La antibodies in sera from patients with inflammatory connective tissue diseases.

SS-B/La antigen was purified by immunoadsorbent columns with immunoglobulin from a patient with primary Sjögren's syndrome. Monitoring of the purification was facilitated by the fused rocket-immunoelectrophoresis technique. Technical ELISA variables for the detection of serum antibodies against the SS-B/La antigen were evaluated, and a recommended procedure is described. Prospective investigation of anti-SS-B/La antibodies in 103 blood donors and 131 patients with chronic inflammatory connective tissue diseases, including 43 patients with primary Sjögren's syndrome was performed. Anti-SS-B/La antibody concentrations were above normal in 65% of the patients with primary Sjögren's syndrome (verified by the strictly objective Copenhagen criteria for keratoconjunctivitis sicca and xerostomia) and 9% of patients with other chronic connective tissue diseases. The predictive value for primary Sjögren's syndrome among patients with increased levels of the anti-SS-B/La antibodies attending a rheumatology clinic was 78%.