Limits...
Identification of a SmD3 epitope with a single symmetrical dimethylation of an arginine residue as a specific target of a subpopulation of anti-Sm antibodies.

Mahler M, Fritzler MJ, Blüthner M - Arthritis Res. Ther. (2004)

Bottom Line: Anti-Sm reactivity is found in 5-30% of SLE patients, depending on the autoantibody detection system and the racial background of the SLE population.In one of those studies, a synthetic dimethylated peptide of SmD1 (amino acids 95-119) exhibited significantly increased immunoreactivity as compared with unmodified SmD1 peptide.These data indicate that anti-SMP antibodies are exclusively present in sera from SLE patients.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dr. Fooke Laboratorien GmbH, Neuss, Germany. m.mahler.job@web.de

ABSTRACT
Anti-Sm antibodies, identified in 1966 by Tan and Kunkel, are highly specific serological markers for systemic lupus erythrematosus (SLE). Anti-Sm reactivity is found in 5-30% of SLE patients, depending on the autoantibody detection system and the racial background of the SLE population. The Sm autoantigen complex comprises at least nine different polypeptides. All of these core proteins can serve as targets of the anti-Sm B-cell response, but most frequently the B and D polypeptides are involved. Because the BB'Sm proteins share cross-reactive epitopes (PPPGMRPP) with U1 specific ribonucleoproteins, which are more frequently targeted by antibodies that are present in patients with mixed connective tissue disease, the SmD polypeptides are regarded as the Sm autoantigens that are most specific to SLE. It was recently shown that the polypeptides D1, D3 and BB' contain symmetrical dimethylarginine, which is a component of a major autoepitope within the carboxyl-terminus of SmD1. In one of those studies, a synthetic dimethylated peptide of SmD1 (amino acids 95-119) exhibited significantly increased immunoreactivity as compared with unmodified SmD1 peptide. Using immobilized peptides, we confirmed that the dimethylated arginine residues play an essential role in the formation of major SmD1 and SmD3 autoepitopes. Moreover, we demonstrated that one particular peptide of SmD3 represents a more sensitive and more reliable substrate for the detection of a subclass of anti-Sm antibodies. Twenty-eight out of 176 (15.9%) SLE patients but only one out of 449 (0.2%) control individuals tested positive for the anti-SmD3 peptide (SMP) antibodies in a new ELISA system. These data indicate that anti-SMP antibodies are exclusively present in sera from SLE patients. Thus, anti-SMP detection using ELISA represents a new serological marker with which to diagnose and discriminate between systemic autoimmune disorders.

Show MeSH

Related in: MedlinePlus

Assay performance characteristics of the anti-SmD3 peptide (SMP) assay. (a) Intra-assay and interassay variability, (b) linearity, and (c) receiver operating characteristic analysis. The intra-assay and interassay variability, expressed as coefficient of variation in percentage (CV%), of three samples ranged from 1.82 to 6.52% and from 2.27 to 7.42%, respectively. Serial dilution series of two samples with high titres of anti-Sm antibodies (S6 and H) exhibited a linear binding response (<20% deviation). Definition of the cutoff, using receiver operating characteristic (ROC) analysis, was performed with SLE and control sera.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC1064884&req=5

Figure 2: Assay performance characteristics of the anti-SmD3 peptide (SMP) assay. (a) Intra-assay and interassay variability, (b) linearity, and (c) receiver operating characteristic analysis. The intra-assay and interassay variability, expressed as coefficient of variation in percentage (CV%), of three samples ranged from 1.82 to 6.52% and from 2.27 to 7.42%, respectively. Serial dilution series of two samples with high titres of anti-Sm antibodies (S6 and H) exhibited a linear binding response (<20% deviation). Definition of the cutoff, using receiver operating characteristic (ROC) analysis, was performed with SLE and control sera.

Mentions: To evaluate the performance of the assay, the precision, reproducibility and linearity were analyzed. The intra-assay and interassay variabilities (coefficient of variation in %) for three samples ranged from 1.82% to 6.52% and from 2.27% to 7.42%, respectively. Even after five serial dilutions, two samples exhibited a linear range of reactivity (<20% deviation). The cutoff was defined by ROC analysis, performed with SLE and control sera. The assay performance characteristics of the new anti-SMP test are summarized in Fig. 2, including intra-assay and interassay variability (Fig. 2a), linearity (Fig. 2b), and ROC analysis, PPV, NPV and efficiency (Fig. 2c).


Identification of a SmD3 epitope with a single symmetrical dimethylation of an arginine residue as a specific target of a subpopulation of anti-Sm antibodies.

Mahler M, Fritzler MJ, Blüthner M - Arthritis Res. Ther. (2004)

Assay performance characteristics of the anti-SmD3 peptide (SMP) assay. (a) Intra-assay and interassay variability, (b) linearity, and (c) receiver operating characteristic analysis. The intra-assay and interassay variability, expressed as coefficient of variation in percentage (CV%), of three samples ranged from 1.82 to 6.52% and from 2.27 to 7.42%, respectively. Serial dilution series of two samples with high titres of anti-Sm antibodies (S6 and H) exhibited a linear binding response (<20% deviation). Definition of the cutoff, using receiver operating characteristic (ROC) analysis, was performed with SLE and control sera.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1064884&req=5

Figure 2: Assay performance characteristics of the anti-SmD3 peptide (SMP) assay. (a) Intra-assay and interassay variability, (b) linearity, and (c) receiver operating characteristic analysis. The intra-assay and interassay variability, expressed as coefficient of variation in percentage (CV%), of three samples ranged from 1.82 to 6.52% and from 2.27 to 7.42%, respectively. Serial dilution series of two samples with high titres of anti-Sm antibodies (S6 and H) exhibited a linear binding response (<20% deviation). Definition of the cutoff, using receiver operating characteristic (ROC) analysis, was performed with SLE and control sera.
Mentions: To evaluate the performance of the assay, the precision, reproducibility and linearity were analyzed. The intra-assay and interassay variabilities (coefficient of variation in %) for three samples ranged from 1.82% to 6.52% and from 2.27% to 7.42%, respectively. Even after five serial dilutions, two samples exhibited a linear range of reactivity (<20% deviation). The cutoff was defined by ROC analysis, performed with SLE and control sera. The assay performance characteristics of the new anti-SMP test are summarized in Fig. 2, including intra-assay and interassay variability (Fig. 2a), linearity (Fig. 2b), and ROC analysis, PPV, NPV and efficiency (Fig. 2c).

Bottom Line: Anti-Sm reactivity is found in 5-30% of SLE patients, depending on the autoantibody detection system and the racial background of the SLE population.In one of those studies, a synthetic dimethylated peptide of SmD1 (amino acids 95-119) exhibited significantly increased immunoreactivity as compared with unmodified SmD1 peptide.These data indicate that anti-SMP antibodies are exclusively present in sera from SLE patients.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dr. Fooke Laboratorien GmbH, Neuss, Germany. m.mahler.job@web.de

ABSTRACT
Anti-Sm antibodies, identified in 1966 by Tan and Kunkel, are highly specific serological markers for systemic lupus erythrematosus (SLE). Anti-Sm reactivity is found in 5-30% of SLE patients, depending on the autoantibody detection system and the racial background of the SLE population. The Sm autoantigen complex comprises at least nine different polypeptides. All of these core proteins can serve as targets of the anti-Sm B-cell response, but most frequently the B and D polypeptides are involved. Because the BB'Sm proteins share cross-reactive epitopes (PPPGMRPP) with U1 specific ribonucleoproteins, which are more frequently targeted by antibodies that are present in patients with mixed connective tissue disease, the SmD polypeptides are regarded as the Sm autoantigens that are most specific to SLE. It was recently shown that the polypeptides D1, D3 and BB' contain symmetrical dimethylarginine, which is a component of a major autoepitope within the carboxyl-terminus of SmD1. In one of those studies, a synthetic dimethylated peptide of SmD1 (amino acids 95-119) exhibited significantly increased immunoreactivity as compared with unmodified SmD1 peptide. Using immobilized peptides, we confirmed that the dimethylated arginine residues play an essential role in the formation of major SmD1 and SmD3 autoepitopes. Moreover, we demonstrated that one particular peptide of SmD3 represents a more sensitive and more reliable substrate for the detection of a subclass of anti-Sm antibodies. Twenty-eight out of 176 (15.9%) SLE patients but only one out of 449 (0.2%) control individuals tested positive for the anti-SmD3 peptide (SMP) antibodies in a new ELISA system. These data indicate that anti-SMP antibodies are exclusively present in sera from SLE patients. Thus, anti-SMP detection using ELISA represents a new serological marker with which to diagnose and discriminate between systemic autoimmune disorders.

Show MeSH
Related in: MedlinePlus