Identification of human Sm and (U1) RNP antigens by immunoblotting.
When HeLa nuclear extracts or ribonucleoproteins (RNPs) from rat liver nuclei were used as antigens, a monospecific anti-(U1)RNP serum recognized in each preparation only 1 polypeptide of 68 or 70 kilodalton (kd) respectively. With a serum of combined anti-Sm/(U1)RNP specificity, HeLa nuclear extracts showed 3 additional antigenic polypeptides of 29, 28, and 16 kd, whereas only 2 additional polypeptides of 27 and 16 kd were observed in rat liver RNPs. However, no antigenic reaction at 68/70 kd was detected with a monospecific anti-Sm serum, indicating that the 68/70 kd antigen is specific for anti-(U1)RNP antibodies. When commercially available ENA extract was used as antigen source only weak immunostaining in the range 70-40 kd and at 16 kd was seen. Elution experiments with anti-Sm antibodies bound to their specific polypeptides demonstrated that neither protein degradation nor cross-reaction was responsible for recognition of the 29/28 and 16 kd antigens by this serum, and that in fact 2 different autoantibody systems are involved.
D000818:Animals; D000936:Antigen-Antibody Complex; D001323:Autoantibodies / Q000032:analysis; D002460:Cell Line; D002467:Cell Nucleus / Q000032:analysis*; D003240:Connective Tissue Diseases / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells / Q000032:analysis; D006801:Humans; D007118:Immunoassay; D008099:Liver / Q000032:analysis; D008180:Lupus Erythematosus, Systemic / Q000235:genetics; D051381:Rats; D012261:Ribonucleoproteins / Q000032:analysis* / Q000276:immunology; D017411:Ribonucleoproteins, Small Nuclear
D000936:Antigen-Antibody Complex; D001323:Autoantibodies; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear