Single Analytes 2

Autoantibodies against

ssDNA | Histones (IgG/IgM) | Scl-70 | CENP | PM-Scl | Jo-1 

ssDNA

Antigen

In 1971, Cohen et al. proposed three categories of antibodies directed against the DNA molecule:

• The first is directed against conformational epitopes associated with the native double-helical structure. By definition, these DNA antibodies are the only true dsDNA antibodies. However, they seem to be rare.
• The second targets the polymers of purine and pyrimidine bases, which as antigens are accessible to the immunocompetent cells only in single-stranded DNA, i.e. in the denatured state. These antibodies are considered the only true ssDNA antibodies.  
• The third targets the desoxyribose-phosphate backbone, which is equally present in ssDNA and dsDNA molecules. Accordingly, they are neither true dsDNA nor true ssDNA antibodies. The majority (85-95%) of DNA antibodies in patient samples belong to this category.

From a technical point of view, it is impossible to measure true ssDNA antibodies (with purine and pyrimidine bases being the sole antigens) in a single test. All ssDNA antibody tests measure DNA antibodies belonging to categories 2 and 3. ssDNA antibodies are commonly found in SLE and drug-induced lupus (DIL). Together with histone antibodies, and in the absence of dsDNA antibodies, they may be an aid in the diagnosis of DIL. They are not specific, however, but also occur in systemic and localized scleroderma, liver disorders, a number of connective tissue diseases and some normal individuals.

In the Varelisa assay, the plate is coated with synthetic single-stranded DNA.

When is the measurement recommended?

Suspicion of SLE or drug-induced lupus.

Antibody isotypes

IgG

Detection methods

Enzyme-linked immunosorbent assays (ELISA).

References

Takehara K et al.  |  Ruffati A et al.  |  Lange A. 

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Histones

Antigen

As an autoimmune disease, SLE is characterized by a complex clinical picture and by a great diversity of autoantibodies. Antibodies against dsDNA and RNP-Sm are the most prominent in the diagnosis of SLE because they demonstrate high specificity for the disease. Of comparable prevalence are antibodies against DNA-binding histone proteins (H1, H2A/H2B, H3 and H4). They can be found in up to 50% of all SLE patient sera. Their frequency increases to 80% in patients with the acute disease. Anti-Histone Antibodies (AHA) are of clinical importance for the diagnosis of drug-induced lupus erythematosus. Drugs such as hydralazine, procainamide and isoniazide are known for their LE-inducing effect. In addition to antibodies against single histones, antibodies against histone complexes such as H2A-H2B and H3-H4 are frequently found in DIL. Depending on the inducing drug, up to 90-95% of DIL patients are positive for histone autoantibodies. However, the test is of limited value because these antibodies are found in other diseases such as infections. AHA have also been found in patients with rheumatoid arthritis, mixed connective tissue disease and progressive scleroderma. However, the incidence of AHA in these patients is low, ranging from 10-15%.

In the Varelisa assay, the plate is coated with purified human histone proteins H1, H2A, H2B, H3 and H4.

When is the measurement recommended?

Suspicion of drug-induced lupus. 

Antibody isotypes

IgG and IgM (measured with mixed conjugate)

Detection methods

Enzyme-linked immunosorbent assays (ELISA).

References

Rubin R.  |  Harmon CE, Portanova JP  |  Shoenfeld Y, Segol O. 

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Scl-70 / DNA topoisomerase I

Promotion material

Antigens

Disease association, antibody prevalence and specificity

• Scleroderma (30-60%), highly specific 
• Anti-Scl-70 do not exclude additional AI disorders such as SLE, Sjögren's syndrome, etc. 
• Not present in relatives of scleroderma patients or other healthy individuals 
• Rarely found in Raynaud's syndrome, but then often as a predictor of scleroderma

Information about scleroderma

Disease activity

When is the measurement recommended?

Antibody isotypes

References

Vazquez-Abad D, Rothfield NF (1996)  |  Verheijen R (1996)  |  Spencer-Green G, Alter D, Welch HG (1997)  |  Hu PQ, Fertig N, Medsger TA, Wright TM (2003) 

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Centromere protein (CENP)

Promotion material

Antigens

The centromere is the primary constriction site of eukaryotic chromosomes where sister chromatids appear most tightly paired. The three main centromere antigens are CENP-A (19 kDa), CENP-B (80 kDa) and CENP-C (140 kDa), the most important being CENP-B. Antibodies to CENP-A and -C are usually cross-reacting and are almost always found in combination with anti-CENP-B antibodies. CENP-B is recognized by virtually all sera with anti-centromere antibodies (ACA).

CENP-B is located within the heterochromatin underneath the kinetochore, and probably forms a dimer that binds DNA and has an important role in regulating higher order chromatin structure within the centromere.

The Varelisa CENP Antibodies assay and the EliA CENP well are coated with human recombinant CENP-B.

Disease association, antibody prevalence and specificity

• CREST (about 55%)  
• Raynaud's disease (10-15%)  
• Diffuse systemic scleroderma (very rarely – ACA in SSc indicate a significantly better prognosis)  
• Other rheumatic conditions with Raynaud's phenomenon, e.g. rheumatoid arthritis, Sjögren's syndrome, etc. (33%)  
• Primary biliary cirrhosis (PBC) (10-20%) 
• Not found in healthy individuals, even in low titres (or extremely rare)

Disease activity

When is the measurement recommended?

Antibody isotype

References

McHugh NJ (1996)  |  Rothfield NF (1996)  |  Spencer-Green G, Alter D, Welch HG (1997)

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PM-Scl   NEW!

Promotion material

EliA PM-Scl (pdf)

Antigens

EliA PM-Scl is coated with human recombinant PM-Scl antigen.

Disease association, antibody prevalence and specificity

• 24% of patients with PM/SSc overlap syndrome
• 8% of patients with polymyositis
• 3% of patients with scleroderma

Prevalence in controls (specificity)

Most papers state a very high specificity. However, frequent co-occurrence in DNA-positive SLE patients is also described.

Indications of a positive PM-Scl result

Approx. 70% of PM-Scl-positive patients have PM/SSc overlap, approx. 20% have idiopathic myositis and approx. 10% have scleroderma.

Disease activity

The antibody usually remains detectable throughout the course of the disease, and indefinitely thereafter despite control of disease activity. Occasionally, the antibody becomes undetectable. The clinical utility of anti-PM-Scl antibody fluctuation requires further investigation.

When is the measurement recommended?

• Suspicion of polymyositis/scleroderma (PM/SSc) overlap syndrome
• Suspicion of systemic sclerosis
• Suspicion of childhood scleromyositis
• Diagnosis/differential diagnosis of myositis of unclear origin

Antibody isotype

References

Conrad K et al (2002)  |  Walker JG, Fritzler MJ (2007)  |  Mahler M et al (2009)  |  Jaskowski TD et al (2011)

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Jo-1/histidyl-tRNA-synthetase 

Promotion material

Performance folder
EliA ANA Differentiation (pdf)
Sm, U1RNP, RNP70, RO, La, Scl-70, CENP, Jo-1

Antigens

Jo-1 is synonymous with histidyl tRNA synthetase. This cytoplasmic enzyme catalyses the esterification of histidine to its cognate tRNA. Binding of anti-Jo-1 antibodies is localized to the cytoplasm of the various cell types examined. Histidyl tRNA synthetase is present as a homodimer within the cell; identical subunits of approximately 50 kDa are each bound to tRNA. Anti-Jo-1 sera only recognize histidyl-tRNA synthetases and no other aminoacyl-tRNA synthetases. They only react with histidyl-tRNA synthetases from higher eukaryotes. The greatest affinity is with the human protein.
The Varelisa Jo-1 Antibodies assay and the EliA Jo-1 well are coated with human recombinant Jo-1.

Disease association, antibody prevalence and specificity

• Adult myositis (about 30%) – almost exclusively in patients with myositis: 54% primary myositis, 40% dermatomyositis, 6% myositis in the setting of another connective tissue disease. Patients with anti-Jo-1 tend to have a severe disease with a tendency to relapse and a poorer prognosis. Anti-synthetase syndrome is defined by antibodies to anti-tRNA synthetase.

• Anti-Jo-1 not in myositis: interstitial lung disease (very rarely)

Disease activity

When is the measurement recommended?

Antibody isotype

References

Maddison PJ (1996)  |  Targoff IN, Plotz PH (1996)  | Delarue M (1995)  |  Targoff IN (1992) 

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