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Sm antibodies target spliceosome components designated U-snRNP (Uridin-rich small nuclear RiboNucleo-Proteins) that play an important role in mRNA processing. The main Sm antigen is the so-called D1 protein contained in U1, U2, U4, U5 and U6-snRNP. Sm antibodies are diagnostic markers (ACR criterion) for SLE, with very high specificity (99 %) but low sensitivity for the disease.

Sm/RNP antibodies are directed against the U1 snRNP complex which is composed of Sm and the three polypeptides of the RNP antigen. Anti-Sm/RNP antibodies are very sensitive markers for Sharp Syndrome. Their sensitivity is 100 %.

The anti-SSA antibodies are directed against SSA (Ro), a protein of 60 kD which belongs to small cytoplasmic ribonucloprotein complexes, the hY-RNP complexes also known as Ro/SSA hY-RNA. These autoantibodies are diagnostic markers and classification criteria for Sjögren’s Syndrome. They are also associated with SLE and Subacute Cutaneous Lupus Erythematosus (SCLE) and present in 90 % of patients with Neonatal Lupus Erythematosus (NLE).

Nucleosome consists of a sequence of DNA wrapped around a Histone octamer. They are responsible of the compactness of DNA in the nucleus.

Following the American College of Rheumatology (ACR), the presence of anti-dsDNA antibodies is one of the diagnostic criteria for Systemic Lupus Erythematosus (SLE). Indeed, they are reported to have a high pathogenic and diagnostic significance for SLE. They are among the most frequently detected autoantibodies associated with SLE. Moreover the dsDNA antibody titer usually correlates with disease activity and dsDNA antibodies are therefore classified as markers of SLE activity.

The M2 antibodies belong to the group of Anti-Mitochondrial Antibodies (AMA) and are strongly associated with PBC. At least 9 distinct AMA have been identified, which have been classified M1-M9 according to their antigen specificity and disease association. Of these, only the M2 subtype approaches absolute specificity for PBC. Indeed, about 95 % of PBC patients have M2 autoantibodies and, conversely, about 90 % of asymptomatic individuals who are found to be M2-positive on routine screening can be shown to have underlying PBC on further investigation.

The M2 antibodies belong to the group of Anti-Mitochondrial Antibodies (AMA) and are strongly associated with PBC. At least 9 distinct AMA have been identified, which have been classified M1-M9 according to their antigen specificity and disease association. Of these, only the M2 subtype approaches absolute specificity for PBC. Indeed, about 95 % of PBC patients have M2 autoantibodies and, conversely, about 90 % of asymptomatic individuals who are found to be M2-positive on routine screening can be shown to have underlying PBC on further investigation.

The M2 antibodies belong to the group of Anti-Mitochondrial Antibodies (AMA) and are strongly associated with PBC. At least 9 distinct AMA have been identified, which have been classified M1-M9 according to their antigen specificity and disease association. Of these, only the M2 subtype approaches absolute specificity for PBC. Indeed, about 95 % of PBC patients have M2 autoantibodies and, conversely, about 90 % of asymptomatic individuals who are found to be M2-positive on routine screening can be shown to have underlying PBC on further investigation.

Centromere antibodies, also called Anti-Centromere Antibodies (ACA), are directed against Centromere-associated Proteins (CENP) and mainly two polypeptides designated CENP-A (19 kD) and CENP-B (80 kD). Antibodies against CENP-A are most of the time detected in combination with antibodies against CENP-B. However, it is reported that CENP-A antibodies can be found in Scleroderma patients before the expression of CENP-B antibodies. The combined detection of CENP-A and CENP-B antibodies is highly specific for systemic sclerosis (diagnostic specificity up to 99 %). With the determination of CENP-A and CENP-B antibodies nearly all of the systemic sclerosis relevant anti-centromere antibody reactivities as seen by indirect immunofluorescence on HEp-2 cells can be detected.

Centromere antibodies, also called Anti-Centromere Antibodies (ACA), are directed against Centromere-associated Proteins (CENP) and mainly two polypeptides designated CENP-A (19 kD) and CENP-B (80 kD). The combined detection of CENP-A and CENP-B antibodies is highly specific for systemic sclerosis (diagnostic specificity up to 99 %). With the determination of CENP-A and CENP-B antibodies nearly all of the systemic sclerosis relevant anti-centromere antibody reactivities as seen by indirect immunofluorescnce on HEp-2 cells can be detected. ACA are also detectable in Primary Biliary Cirrhosis (PBC) patients. In this case, half of the patients have also a Scleroderma.