Dissociation of immune responses to the SS-A (Ro) 52-kd and 60-kd polypeptides in systemic lupus erythematosus and Sjögren's syndrome.
The cellular RNA particle SS-A (Ro) is a target of autoimmune response in many patients with Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE). Recent immunologic, biochemical, and DNA cloning studies have shown that the SS-A particle consists of at least 2 polypeptide components, of 52 kd and 60 kd. Immunodiffusion analysis of 60 sera from patients with primary SS revealed 47 (78%) to be SS-A precipitin positive. Western blotting studies of the sera showed 3 groups of reactivities: 22 (47%) possessed autoantibodies against both the 60-kd and the 52-kd polypeptides, 19 (40%) reacted only with the 52-kd protein, and 6 (13%) were nonreactive in Western blots although positive in immunodiffusion. Fifty-one of 90 SLE sera (57%) were SS-A precipitin positive by immunodiffusion. In Western blots, 24 (47%) possessed antibodies against both the 60-kd and the 52-kd antigens, while 9 (18%) reacted only with the 60-kd protein. Eighteen (35%) were nonreactive by Western blot, although positive by immunodiffusion. Antibody to the 52-kd antigen without concomitant antibody to the 60-kd antigen was seen only in patients with primary SS, whereas antibody to the 60-kd antigen without concomitant antibody to the 52-kd antigen was seen only in SLE patients. Although antibodies to SS-A are detected in both SS and SLE, our findings show that there is dissociation of immune responses to the 2 component antigens of the particle, which may be evidence of different events initiating the autoimmune process in these diseases.
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W.M. Keck Autoimmune Disease Center, Department of Basic and Clinical Research, Scripps Clinic, La Jolla, California 92037.
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D000917:Antibody Formation / Q000502:physiology*; D001324:Autoantigens / Q000032:analysis / Q000276:immunology*; D001327:Autoimmune Diseases / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D015153:Blotting, Western; D006801:Humans; D005779:Immunodiffusion; D008180:Lupus Erythematosus, Systemic / Q000276:immunology* / Q000473:pathology / Q000503:physiopathology; D008970:Molecular Weight; D010455:Peptides / Q000032:analysis / Q000276:immunology; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D012859:Sjogren's Syndrome / Q000276:immunology* / Q000473:pathology / Q000503:physiopathology; D000099207:SS-A Antigen
D001324:Autoantigens; D010455:Peptides; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D000099207:SS-A Antigen; C116006:RO60 protein, human