Screening for autoantibodies to the nucleolar U3- and Th(7-2) ribonucleoproteins in patients' sera using antisense riboprobes

In this study we report the detection of autoantibodies to the nucleolar U3- and Th(7-2) ribonucleoprotein (RNP) particles in sera from patients with connective tissue diseases. The method described employs radioactively labelled antisense U3- and Th RNA which are hybridized to immunoprecipitated U3- or Th RNA from a HeLa cell extract. Of the 66 sera that were screened with this method seven sera (11%) precipitated only Th RNP, 16 sera (24%) precipitated only U3 RNP and 4 sera (6%) precipitated both U3- and Th RNP. Both anti-U3 RNP and anti-Th RNP activity appeared to be mostly associated with scleroderma or scleroderma-associated diseases. Using this method we also showed that some of the TH RNP particles in a cell extract are associated with the La autoantigen. We conclude that for the identification of immunoprecipitated RNAs this method is very sensitive and provides unambiguous data.