LAUSR

OBJECTIVE To develop a multianalyte assay for the detection of dermatomyositis (DM)-related autoantibodies using immunoprecipitation (IP) combined with immunoblotting (IB). METHODS Sera from 116 DM patients were subjected to RNA and protein immunoprecipitation assays as well as commercial enzyme-linked immunosorbent assays (ELISAs) for anti-aminoacyl tRNA synthetase, anti-melanoma differentiation antigen 5 (MDA5), anti-Mi-2, anti-transcriptional intermediary factor-1γ (TIF-1γ), and anti-U1 ribonucleoprotein antibodies. The IP/IB assay was developed by immunoprecipitation of autoantigens from HeLa cell extracts using patient sera, followed by immunoblotting with an antibody against Mi-2, TIF-1γ, OJ, nuclear matrix protein (NXP)-2, MDA5, PM/Scl, small ubiquitin-like modifier activating enzyme (SAE), or Ku. A multianalyte assay was designed by mixing primary antibodies in the IP/IB assay. RESULTS IP assays identified any DM-related autoantibodies in 100 patients (86%), of which 82% were covered by commercial ELISAs, with a false-positive result in two sera and a false-negative result in one. The results obtained from the multianalyte IP/IB assay and 'gold-standard' IP assays were concordant in terms of the presence or absence of anti-MDA5, anti-TIF-1γ, anti-OJ, anti-NXP-2, anti-PM/Scl, anti-SAE, anti-Mi-2, and anti-Ku antibodies. CONCLUSION This multianalyte IP/IB assay combined with commercial ELISAs is an alternative to 'gold-standard' IP assays for the detection of DM-related autoantibodies.