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1.
Arthritis Rheum ; 40(4): 661-71, 1997 Apr.
Article in English | MEDLINE | ID: mdl-9125248

ABSTRACT

OBJECTIVE: To define the epitope-recognition pattern and the fine specificity of the autoantibody response to protein L7 in patients with rheumatic diseases. METHODS: The epitope-recognition pattern was studied by enzyme-linked immunosorbent assay utilizing overlapping fragments of L7. The fine specificity was examined by binding inhibition and isoelectric focusing. RESULTS: We observed a disease-specific epitope-recognition pattern of anti-L7 autoantibodies. There was one immunodominant epitope that was recognized by all anti-L7-positive sera from patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and systemic sclerosis (SSc). Additional recognition of minor epitopes was observed; it arises by intramolecular epitope spreading and was correlated with disease activity in SLE patients. SSc patients differed from SLE and RA patients in that their sera did not recognize certain minor epitopes. The major epitope was recognized by high-affinity autoantibodies of limited heterogeneity. Minor epitopes were recognized by heterogeneous low-affinity autoantibodies. CONCLUSION: The anti-L7 autoantibody response is oligoclonal. Additional B cell clones are activated by antigen during active phases of disease.


Subject(s)
Autoantibodies/analysis , Autoimmune Diseases/immunology , Epitope Mapping , Epitopes/immunology , Ribosomal Proteins/immunology , Adolescent , Arthritis, Rheumatoid/immunology , Enzyme-Linked Immunosorbent Assay , Female , Humans , Isoelectric Focusing , Lupus Erythematosus, Systemic/immunology , Peptide Fragments/immunology , Scleroderma, Systemic/immunology , Sensitivity and Specificity
2.
Clin Exp Immunol ; 100(2): 198-204, 1995 May.
Article in English | MEDLINE | ID: mdl-7743655

ABSTRACT

Recent studies have shown that sera of patients suffering from systemic autoimmune diseases contain autoantibodies directed against the eukaryotic ribosomal protein L7 [1]. In the present study we screened a large panel of sera from patients with systemic lupus erythematosus (SLE) for the presence of anti-L7 autoantibodies and their relationship to clinical, serological and genetic parameters of SLE. By means of an ELISA employing recombinant protein L7 as antigen we detected anti-L7 autoantobodies in 172 of 506 SLE sera (34%). Negative correlations were observed between the presence of anti-L7 autoantibodies, serum IgG levels and proteinuria; a potentially positive relationship existed with lung fibrosis. In order to analyse further this possibility we screened sera of 129 patients suffering from progressive systemic sclerosis (PSS) for anti-L7 reactivity; 45 of these patients had lung fibrosis. Of the PSS patients, 41% exhibited anti-L7 autoantibodies, but positive reactions were evenly distributed among patients with and without lung fibrosis. Protein L7 thus represents a major autoantigen of systemic autoimmune diseases, but does not so far define a distinct subpopulation of patients.


Subject(s)
Autoantibodies/immunology , Lupus Erythematosus, Systemic/immunology , Ribosomal Proteins/immunology , Scleroderma, Systemic/immunology , Autoantigens/immunology , Humans , Recombinant Proteins
3.
Clin Exp Immunol ; 100(2): 205-13, 1995 May.
Article in English | MEDLINE | ID: mdl-7743656

ABSTRACT

Ribosomal protein L7 has been established recently as a novel autoantigen representing a frequent target for autoantibodies from patients with systemic autoimmune diseases. Up to 75% of systemic lupus erythematosus (SLE) patients and 50% of mixed connective tissue disease (MCTD) and progressive systemic sclerosis (PSS) patients produce antibodies in vitro translated L7 and form immunoprecipitable complexes. In this study the B cell response to protein L7 was investigated with respect to the immunogenic determinants recognized by autoantibodies. Eighteen truncated fragments of protein L7 were generated as recombinant fusions with glutathione-S-transferase and examined by immunoblotting for their reactivity with sera from patients suffering from systemic rheumatic diseases. Anti-L7 antibodies target three major nonoverlapping autoepitopes. Two epitopes reside in the highly conserved C-terminal part of the protein, whereas the N-terminal autoepitope is not conserved during evolution. The N-terminal epitope comprises 24 amino acid residues. Ten amino acid resides of this epitope are shared with the BZIP-like RNA binding domain of protein L7. Autoantibodies recognizing this epitope crossreact with the corresponding region of a L7 homologue, namely ribosomal protein L7 (RPL7) from Dictyostelium discoideum. This indicates that amino acid residues 14VPE...KKR22, which are conserved between humans and fungi, contribute essentially to the formation of autoantibody-autoantigen complexes.


Subject(s)
Autoantigens/immunology , Ribosomal Proteins/immunology , Amino Acid Sequence , Animals , Cross Reactions , Dictyostelium/immunology , Epitope Mapping , Humans , Molecular Sequence Data , RNA-Binding Proteins/immunology , Recombinant Proteins , Sequence Alignment , Sequence Homology, Amino Acid
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