Detection of SS-A/Ro and SS-B/La Autoantibodies Using Immunoblotting Procedure and Characterization of the Antigens from 293 Cells and KB Cells
Specific and sensitive assay was performed to detect both antiSS-A/Ro and antiSS-B/La antibodies in sera of patients with collagen diseases including SLE, PSS, etc. The SS-A/Ro and SS-B/La antigens were prepared from human spleen (HSE) and cultured human cell line (KB cells), while rabbit thymus extract (RTE) was used as SS-B/La antigen marker. The antigens were partially purified by DEAE cellulose column chromatography. The SS-A/Ro antibody was shown to react mainly with 58KDa peptide by means of immunoblotting. Sera containing both the SS-A/Ro and SS-B/La antibody reacted with 40KDa peptide of RTE, and 58KDa, 42KDa and 40KDa peptides of HSE. We found that some of SS-A/Ro antisera could further react with 64KDa peptide in HSE. The 58KDa peptide is rich in a cytoplasmic fraction of KB cells, and the 40KDa peptide in the nucleoplasmic fraction. KB cells are not less good source of the antigens than human spleen. Extracts of 293 cells (human embryonic kidney cells expressing adenovirus-5 El gene) were prepared by the same method from KB cells, though immunoblotting patterns of both SS-A/Ro and SS-B/La antigens of 293 cell extracts are similar to those of KB cells, the relative content of SS-B/La antigens in 293 cell extracts are decreased.