[Purification of the Ro/SSA antigen and enzyme-linked immunosorbent assay for quantitation of the antibody].

Antibodies to the Ro/SSA antigen occur in patients with Sjögren's syndrome and other collagen diseases. In this study, we used ammonium sulfate precipitation, anti-Ro/SSA immunoaffinity chromatography and gel filtration to purify the Ro/SSA antigen from pig spleen. In addition, the normal human IgG affinity column chromatography was also used to adsorb nonspecific reacting materials as heterophile antigens which contaminated in preparations after immunoaffinity chromatography. On SDS-PAGE the purified Ro/SSA antigen migrated as 60K and 53K polypeptides bands and the antigenicity was observed on 60 K band. An enzyme-linked immunosorbent assay (ELISA) using the purified antigen was developed for quantitation of the antibody which was found to be sensitive, precise and specific. By the method, anti-Ro/SSA antibodies were detected in SLE (44%), MCTD (71%), PSS (50%), SjS (83%), RA (16%), PBC (23%), lupoid hepatitis (23%) but only 4% in normal controls. The purified antigen and ELISA method will provide beneficial tools for the investigation of autoimmune diseases.