Implications of anti-Ro/Sjögren's syndrome A antigen autoantibody in normal sera for autoimmunity.
We have applied a sensitive assay to analyze lupus and Sjögren's syndrome autoantibodies in 40 normal sera. Seven of these bound Ro/Sjögren's syndrome A antigen (SSA). Although this binding was 1,000-fold lower than the highest anti-Ro/SSA level measured from patients, it was inhibited by human Ro/SSA. Positive normal serum-bound Ro/SSA in Western immunoblots and binding activity was demonstrated in the F(ab')2 fragment of IgG. Affinity purification of normal anti-Ro/SSA IgG increased the specific anti-Ro/SSA binding by greater than 17-fold. This purified antibody formed a Ro/SSA precipitin and had a relative affinity for Ro/SSA identical to that of Ro/SSA precipitin-positive patients. These data demonstrate that the anti-Ro/SSA present in healthy normal donors is true autoantibody. Anti-La/Sjögren's syndrome B antigen (SSB) autoantibodies were found in 3 of the 40 normal sera, while none bound nuclear ribonucleoprotein (Sm). Finding low levels of anti-Ro/SSA and anti-La/SSB among normals may indicate that anti-Ro/SSA and anti-La/SSB occur in disease by enhancement of a preexisting immune response.
D000328:Adult; D001323:Autoantibodies / Q000032:analysis* / Q000276:immunology; D001324:Autoantigens / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D007163:Immunosorbent Techniques; D008297:Male; D008875:Middle Aged; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D000097585:SS-B Antigen; D000099207:SS-A Antigen
D001323:Autoantibodies; D001324:Autoantigens; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D000097585:SS-B Antigen; D000099207:SS-A Antigen; C116006:RO60 protein, human