THE RECOGNITION OF HUMAN 60-KDA RO RIBONUCLEOPROTEIN-PARTICLES BY ANTIBODIES ASSOCIATED WITH CUTANEOUS LUPUS AND NEONATAL LUPUS

The hY RNAs form a macromolecular complex with the 60-kDa Ro protein a nd may in addition be bound by the La protein. In this study, we exami ne the autoantibody responses to the intact protein-RNA complexes in 1 8 subacute cutaneous lupus (SCLE), 10 discoid lupus (DLE), and 18 neon atal lupus erythematosus (NLE) sera. All SCLE and NLE serum samples pr ecipitated all four of the Ro hY RNAs, whereas none of the DLE serum s amples precipitated the hY RNAs. Among the SCLE and NLE sera, there wa s a significant association between the amount of Ro hY RNAs precipita ted and the concurrent presence of anti-La antibodies in the sera (p = 0.008), consistent with the hypothesis that both the 60-kDa Ro and th e La proteins can bind the Ro hY RNAs. There was no correlation betwee n the amount of hY RNAs precipitated and the titer of antibodies to th e 60-kDa Ro protein in enzyme-linked immunosorbent assay (ELISA). This may be due to a difference in the epitopes formed by the antigen in t he respective assays. The autoantibody response to Ro in SCLE and NLE, which is generally detectable by both immunodiffusion and ELISA, is d irected to all the subsets of the Ro protein-hY RNA complexes. The aut oantibody response in DLE, though frequently detectable by ELISA, is n ot of sufficient concentration or affinity to precipitate the Ro prote in-RNA complexes. The autoantibody response to Ro in SCLE and NLE may include antibodies to epitopes created by the complexing of the 60-kDa Ro protein with hY RNA.