A major, novel systemic lupus erythematosus autoantibody class recognizes the E, F, and G Sm snRNP proteins as an E-F-G complex but not in their denatured states.
OBJECTIVE
To determine whether the E, F, and G Sm proteins present antigenic determinants recognized by systemic lupus erythematosus (SLE) patient sera, and if so, whether the antigenicity depends on the native conformations of the polypeptides and/or is E-F-G complex restricted.


METHODS
Radioimmunoprecipitation, epitope tagging, expression polymerase chain reaction, in vitro translation, in vitro reconstitution, and immunoblotting.


RESULTS
Most of the anti-Sm SLE patient sera tested reacted with one or more of the E, F, and G proteins in immunoprecipitation studies but not on immunoblots. All sera, however, highly efficiently immunoprecipitated the E-F-G complex. This complex recognition was detected exclusively in anti-Sm patient sera but not in patient sera with other serotypes.


CONCLUSIONS
We demonstrate the presence of a novel and abundant anti-Sm autoantibody class in SLE patient sera which exclusively or predominantly recognizes conformational Sm epitopes present on the E-F-G complex but not on the denatured proteins. This complex recognition is highly specific for sera of the anti-Sm serotype and may be relevant for clinical diagnosis as well as for understanding the etiology of anti-Sm autoantibody production.
Brahms
H
H
Institut für Molekularbiologie und Tumorforschung, Philipps-Universität Marburg, Germany.
Raker
V A
VA
van Venrooij
W J
WJ
Lührmann
R
R
D001323:Autoantibodies / Q000145:classification* / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology* / Q000378:metabolism; D015153:Blotting, Western; D017931:DNA Primers / Q000737:chemistry; D000939:Epitopes / Q000276:immunology*; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000175:diagnosis / Q000276:immunology*; D010455:Peptides / Q000276:immunology; D016133:Polymerase Chain Reaction; D011233:Precipitin Tests; D011489:Protein Denaturation; D017411:Ribonucleoproteins, Small Nuclear / Q000276:immunology*; D055517:snRNP Core Proteins
D001323:Autoantibodies; D001324:Autoantigens; D017931:DNA Primers; D000939:Epitopes; D010455:Peptides; D017411:Ribonucleoproteins, Small Nuclear; D055517:snRNP Core Proteins