Detection of autoantibodies to ribonucleoproteins by counter-immunoelectropheresis, immunoblotting and RNA-immunoprecipitation: comparison of results.

Counterimmunoelectropheresis (CIE), immunoblotting (IB) and RNA-immunoprecipitation (RNA-IP) were compared for their potential to detect antibodies to U1RNP, Sm and SS-B in sera from 50 patients with SLE and 18 with MCTD. Anti-SS-B were detected in 6 SLE-sera (12%) and one MCTD-serum (6%) by all three techniques. Anti-Sm were present in 7 SLE-sera (14%) by RNA-IP and IB; 3 of these sera showed identity with a-Sm and 4 with a-U1RNP by CIE. Antibodies precipitating U1RNA were present in 8 SLE sera (16%); 4 of these sera were positive for anti-U1RNP by CIE (8%) and 4 sera recognized one or more of the U1RNA-associated proteins by IB (8%). All MCTD-sera were positive for anti-U1RNP by RNA-IP including one serum negative by IB and CIE. RNA-IP allowed the detection of antibodies precipitating U1-U2RNA in 4 sera; in IB, the U2RNA specific protein B" was recognized by 3 sera. RNA-IP appears to be a sensitive method for detecting anti-URNP's.