title: Detection by ELISA of antibodies to small RNA protein particles in systemic lupus erythematosus patients whose sera lack precipitins.
abstract: Three hundred five consecutive patients with systemic lupus erythematosus (SLE) have been evaluated for antibodies to the RNA protein particles, Sm, nRNP, Ro/SSA, and La/SSB. Precipitating antibodies were found in 224 (73.1%). With the use of ELISA methodology with affinity-purified antigens, 76 sera from precipitin-negative patients were assayed and 35 had elevated levels of one or more of the autoantibodies. Of these, 27 (36%) had elevated anti-nRNP and 17 (22%) had elevated anti-Ro/SSA. Six of the seven patients with anti-La/SSB (18%) also had anti-Ro/SSA paralleling the close association of these two antibodies noted by precipitin analysis in which 38 of 39 patients with anti-La/SSB precipitins also have anti-Ro/SSA precipitins. Thus, 258 of the 305 SLE sera (84.6%) have elevated anti-RNA protein levels. This represents a minimum estimate of the frequency of these antibodies since longitudinal study of individual patients shows that anti-RNA protein levels may vary from normal to 1000 times over background at different times. Quantitative studies over time in two patients with both anti-Sm and anti-nRNP show that anti-nRNP increased 10- to 100-fold while anti-Sm changed little. These quantitative changes may relate to clinical phenomena.
mesh_terms: D000293:Adolescent; D000328:Adult; D000974:Antibodies, Antinuclear / Q000302:isolation & purification*; D001324:Autoantigens / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D008181:Lupus Nephritis / Q000276:immunology; D008297:Male; D011234:Precipitins / Q000302:isolation & purification; D012261:Ribonucleoproteins / Q000276:immunology; D017411:Ribonucleoproteins, Small Nuclear; D055517:snRNP Core Proteins
chemical_list: D000974:Antibodies, Antinuclear; D001324:Autoantigens; D011234:Precipitins; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear; C035356:SS-A antibodies; C035357:SS-B antibodies; D055517:snRNP Core Proteins