Comparison of five methods for the detection of antiribosomal P protein antibody

1. We have compared the sensitivity and specificity of immunofluorescence, counterimmunoelectrophoresis, immunodiffusion, Western blotting and ELISA for the detection of antiribosomal P protein antibodies using 153 lupus sera. 2. Western blotting and ELISA were the 2 most sensitive and specific techniques for the detection of these antibodies. In contrast, cytoplasmic immunofluorescence was observed in only one third of the anti-P-positive patients. Immunodiffusion and counterimmunoelectrophoresis, although highly specific, detecting 14 per cent and 29 per cent of all anti-P-positive sera by Western blotting, were the least sensitive tests. 3. The frequency of anti-P in lupus patients, as detected by Western blotting analysis was 18 per cent . The most frequently observed antibody in anti-P sera was anti-Ro/SSA (39 per cent ). Anti-P antibodies were also detected in the sera of 3 patients with negative nuclear immunofluorescence. 4. Anti-P is an additional serological marker for systemic lupus erythematosus and Western blotting is the method of choice for detecting this antibody due to the limited availability of the fusion protein in Brazil

Antibodies to new cytoplasmic autoantigens: anti-ja, a potential marker for disease activity in systemic lupus erythematosus

We describe new autoantibodies which recognize two cytoplasmic proteins of 30 and 26 kDa. They were detected by Western blot analysis in the sera of 6 of 79 randomly selected systemic lupus erithematosus (SLE) patients and are denoted anti-JA antibodies. This antibody specificity is different from the previously described lupus autoantibodies, anti-P and anti-S10. The targeted autoantigens are trypsin sensitive, and resistant to RNase and DNase treatment. The binding to the antigens was not modified when reticulocyte ribosomes were prepared with protease inhibitors indicating that these are primary antigen and not degradation products. Several lines of evidence suggest that these proteins are almost certainly part of the ribosome. Anti-JA reactivity was not observed in the sera from 60 patients with other autoimmune diseases or from normal individulas. In contrast, 55% of lupus sera selected for a high titer of anti-ds DNA (double stranded DNA) and LE cells were also anti-JA positive. Anti-JA antibodies may be useful as a specific serological marker for disease activity in SLE. The strong association with anbti-ds-DNA antibodies and LE cell in the sera of SLE patients requires further study