Antibodies from patients with rheumatoid arthritis and systemic lupus erythematosus recognize different epitopes of a single heterogeneous nuclear RNP core protein. Possible role of cross-reacting antikeratin antibodies.
Antibodies to recombinant heterogeneous nuclear RNP core protein A1 were detected in sera from 27 of 58 patients with rheumatoid arthritis (RA) and from 7 of 31 patients with systemic lupus erythematosus, by immunoblotting and enzyme-linked immunosorbent assay. Protein A1 consists of 2 distinct domains: The N-terminal sequence is identical to a single-stranded DNA binding protein termed UP1, and the C-terminal domain shows a partial homology with keratin. All 7 A1-positive systemic lupus erythematosus sera reacted with UP1, whereas 9 of the 27 A1-positive RA sera did not. In RA, anti-A1 activity was significantly associated with antikeratin antibodies (AKA); these antibodies were present in 23 of 27 A1-positive sera and 10 of 31 A1-negative sera (P less than 0.01). Immunoabsorption with recombinant protein A1 resulted in a significant reduction of AKA titers in 6 of 10 RA sera tested, suggesting that AKA from RA patients may cross-react with the C-terminal portion of the heterogeneous nuclear RNP protein A1.
Istituto di Patologia Medica, IRCCS Policlinico S. Matteo, University of Pavia, Italy.
C
C
Montecucco
R
R
Caporali
C
C
Negri
F
F
de Gennaro
A
A
Cerino
M
M
Bestagno
F
F
Cobianchi
G C
GC
Astaldi-Ricotti
D000293:Adolescent; D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D001323:Autoantibodies / Q000032:analysis / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology*; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D005260:Female; D006801:Humans; D015151:Immunoblotting; D007633:Keratins / Q000276:immunology*; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009687:Nuclear Proteins / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D014758:Viral Core Proteins / Q000276:immunology; D055517:snRNP Core Proteins
D001323:Autoantibodies; D001324:Autoantigens; D000939:Epitopes; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D014758:Viral Core Proteins; D055517:snRNP Core Proteins; D007633:Keratins