Detection and occurrence of the 60‐ and 52‐kD Ro (SS‐A) antigens and of autoantibodies against these proteins

• Published in: Clinical and experimental immunology 1991-10, Vol.86 (1), p.99-105
• Main Authors: SLOBBE, R. L., PRUIJN, G. J. M., DAMEN, W. G. M., KEMP, J. W. C. M., VENROOIJ, W. J.
• Format: Article
• Language: English
• Subjects: Antibody Specificity; Autoantibodies - analysis; autoantigen autoantibodies; Autoantigens - analysis; Autoimmune Diseases - immunology; Electrophoresis, Polyacrylamide Gel; Humans; Molecular Weight; Nuclear Proteins - immunology; Ribonucleoproteins - immunology; RNA, Small Cytoplasmic; Ro (SS‐A); Sjogren's syndrome; Species Specificity; SS-B Antigen; systemic lupus erythamatosus; Tumor Cells, Cultured
• ISSN: 0009-9104; 1365-2249
• DOI: 10.1111/j.1365-2249.1991.tb05780.x

SUMMARY The simultaneous detection of anti‐La. anti‐60‐kD Ro and anti‐52‐kD Ro antibodies by immunoblotting is greatly improved by changing the erosslinking level in the gel to an acrylamide/bisacrylamide ratio of 19:1. Using this method for the analysis of a number of systemic lupus erythematosus (SLE) and Sjögren's syndrome patient sera it was observed that antibody to the 52‐kD Ro protein without anti‐60‐kD Ro antibody was restricted to Sjogren's syndrome patients (9/26), whereas antibody to the 60‐kD Ro protein without contaminating anti‐52‐kD Ro antibody was only found in SLE patients (8/38). Moreover, in Sjogren's sydrome patient sera anti‐Ro antibody was found only in combination with anti‐La antibody (20/26). whereas in SLE patient sera anti‐Ro antibody could be found without detectable anti‐La specificity (4/38). Double immunofluorescence microscopy revealed that the 52‐kD Ro and the 60‐kD Ro proteins co‐localize in the cytoplasm as well as in the nucleus, whereas immunoprecipitation of [32P]‐labelled HeLa cell extract with monospecific anti‐52‐kD Ro and anti‐60‐kD Ro sera showed that both proteins are associated with the Ro RNAs. These data suggest the presence of both the 52‐kD and the 60‐kD Ro proteins in the same ribonucleoprolein complexes. To study the evolutionary conservation of the 52‐kD Ro, the 60‐kD Ro and the La proteins, extracts of cell lines derived from various mammalian species were analysed on Western blols using monospecific human antibodies. In contrast to the 60‐kD Ro and the La antigens which are well conserved in evolution, the 52‐kD Ro antigen could be detected in primate cells only by this immunological approach.