Anti-Ro52 reactivity is an independent and additional serum marker in connective tissue disease.
OBJECTIVE
To determine whether anti-Ro52 is an independent serum marker in connective tissue disease.


METHODS
Over a two year period, 1727 consecutive antinuclear antibody (ANA) positive serum samples were analysed in parallel by double immunodiffusion with thymus/spleen nuclear extract and by line immunoassay with recombinant Ro52, recombinant La/SSB, and natural Ro60. Sera that were only reactive towards Ro52 were further analysed by a variety of additional anti-SSA/Ro detection methods and by specific anti-Ro52 and anti-Ro60 assays. Natural purified SSA/Ro was analysed by immunoblot and protein sequencing.


RESULTS
Analysis of natural purified SSA/Ro (Immunovision, Springdale, AR) showed only Ro60 and no immunoreactive Ro52. Consequently, assays based on this substrate only identify sera with anti-Ro60 reactivity. Twenty serum samples showed anti-Ro52 without anti-Ro60 and anti-SSB/La on line immunoassay. By additional testing, 2/20 sera were found positive for anti-Ro60 reactivity. The remaining 18 sera were not identified by any of the classical anti-SSA/Ro assays and were considered to be reactive only with Ro52 and not with Ro60. This anti-Ro52 reactivity was confirmed by natural and recombinant Ro52 in 16/18 cases. 12/18 sera corresponded to connective tissue diseases.


CONCLUSIONS
Anti-Ro52 positive sera without any evidence of anti-Ro60 and anti-La/SSB reactivity can be considered as an independent group that is systematically missed by classical anti-SSA/Ro detection methods owing to a bias towards anti-Ro60 reactivity. The anti-Ro52 sera are precipitin negative, not retrieved by SSA/Ro enzyme linked immunosorbent assays (ELISAs) based on natural SSA/Ro, and show no specific ANA fluorescence staining pattern. These findings together with the clinical data indicate that anti-Ro52 should be considered as an additional and independent serum marker.
Peene
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I
Department of Rheumatology, University Hospital Gent, Belgium Innogenetics, Gent, Belgium Centre Hospitalier Luxembourg, Luxembourg. filip.dekeyser@rug.a.be
Meheus
L
L
De Keyser
S
S
Humbel
R
R
Veys
E M
EM
De Keyser
F
F
D000974:Antibodies, Antinuclear / Q000097:blood*; D001324:Autoantigens / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D003240:Connective Tissue Diseases / Q000097:blood* / Q000175:diagnosis; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D020733:RNA, Small Cytoplasmic; D011994:Recombinant Proteins / Q000276:immunology; D012261:Ribonucleoproteins / Q000276:immunology*; D000099207:SS-A Antigen
D000974:Antibodies, Antinuclear; D001324:Autoantigens; D015415:Biomarkers; D020733:RNA, Small Cytoplasmic; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; D000099207:SS-A Antigen; C116006:RO60 protein, human