Detection and occurrence of the 60- and 52-kD Ro (SS-A) antigens and of autoantibodies against these proteins.
The simultaneous detection of anti-La, anti-60-kD Ro and anti-52-kD Ro antibodies by immunoblotting is greatly improved by changing the crosslinking 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 Sjögren'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 Sjögren's syndrome 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 ribonucleoprotein 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 blots 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.
Department of Biochemistry, University of Nijmegen, The Netherlands.
R L
RL
Slobbe
G J
GJ
Pruijn
W G
WG
Damen
J W
JW
van der Kemp
W J
WJ
van Venrooij
D000918:Antibody Specificity; D001323:Autoantibodies / Q000032:analysis*; D001324:Autoantigens / Q000032:analysis*; D001327:Autoimmune Diseases / Q000276:immunology*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000276:immunology; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins / Q000276:immunology; D013045:Species Specificity; D014407:Tumor Cells, Cultured; D000097585:SS-B Antigen; D000099207:SS-A Antigen
D001323:Autoantibodies; D001324:Autoantigens; D009687:Nuclear Proteins; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D000097585:SS-B Antigen; D000099207:SS-A Antigen; C116006:RO60 protein, human