Clinical needs often dictate testing for several autoantibodies in a single patient with evidence of autoimmune disease. We developed a microarray containing 15 autoantigens for the detection of autoantibodies in rheumatoid autoimmune diseases.
We synthesized recombinant centromere protein B, cytokeratin 19, SSA 52-kDa antigen, SSA 60-kDa antigen, SSB antigen, and Jo-1 antigen and prepared anti-nuclear antibody antigens. Cyclic citrullinated peptide, histone, goat IgG for detection of rheumatoid factor, double-stranded DNA, and single-stranded DNA were purchased, as were recombinant small nuclear ribonucleoprotein U1, topoisomerase I, and Smith antigen (Sm). All 15 antigens were of human origin except calf thymus Sm. Proteins were printed on polystyrene. The arrays were incubated with serum samples and then with horseradish peroxidase-conjugated secondary antibodies and chemiluminescent substrates, and light signals were captured by a charge-coupled device camera-based chip reader. Antibodies were quantified by use of calibration curves. Positive samples were confirmed by commercially available methods.
The detection limit of the microarray system was 20 pg of IgG printed on the polystyrene support. More than 85% of the confirmed positive sera were detected as positive with the microarray system based on cutoff values established with the microarray system. The imprecision (CV) of the microarrays was <15% for all 15 autoantibody assays, with the exception of single-stranded DNA (18% and 23%) within and between batches. Characteristic autoantibody patterns were seen in patients with clinical diagnoses of rheumatoid arthritis (n = 83), systemic lupus erythematosus (n = 71), systemic sclerosis (n = 36), polymyositis (n = 38), and Sjogren syndrome (n = 20).
This microarray system provides results similar to those by conventional methods. Assessment of the diagnostic accuracy of the system remains to be done.