Antiscleroderma-70 Antibodies

Laboratory assay overview

Detect antibodies associated with SLE and mixed connective tissue disease. Sm antibodies are highly specific for SLE. RNP antibodies are found with a variety of rheumatoid diseases. RNP, Sm, SS-A, SS-B, Scl-70, and Jo-1 are extractable nucleoprotein complexes found in the nucleus and/or cytoplasm of substrate cells. Autoantibodies to the ribosomal P protein represent a highly specific marker for the diagnosis of SLE, where they have been associated with certain clinical manifestations. The native protein SmRNP contains two different regions: Sm and RNP that are different regions of the same macromolecule. SmRNP is the best antigen for detection of antibodies to either Sm or RNP but cannot discriminate between the antibody specificities. Inclusion of SmRNP increases sensitivity while inclusion of Sm and RNP increases specificity.

Laboratory assay overview

Detect antibodies associated with SLE and mixed connective tissue disease. Anti-Sm is highly specific for SLE. Anti-RNP is found with a variety of rheumatoid diseases. RNP, Sm, SS-A, SS-B, Scl-70, and Jo-1 are extractable nucleoprotein complexes found in the nucleus and/or cytoplasm of substrate cells.

Laboratory assay overview

Differential diagnosis of scleroderma (progressive systemic sclerosis)

Laboratory assay overview

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular abnormalities, and cutaneous and visceral fibrosis. Some antibodies are considered highly specific for SSc, including Scl-70 (anti-topoisomerase 1) antibody, anti-centromere (CENP) antibodies, and anti-RNA polymerase III antibody and are classification criteria for disease defined by the American College of Rheumatology. Centromere antibodies are found in patients with a limited form of cutaneous systemic sclerosis, "CREST" syndrome, a complex of subcutaneous calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasias. RNA polymerase III antibodies target RNAP III epitopes 11 and 155. Antibodies to three major components of U1-snRNP (snRNP RNP A, U1-snRNP RNP C, U1-snRNP RNP-70kd): U1- are associated with scleroderma and inflammatory myopathy overlap syndromes. Anti-fibrillarin (anti-U3RNP) antibodies are associated with diffuse cutaneous SSc, frequent visceral involvement, and especially renal and cardiac involvement. In African-American patients, anti-fibrillarin antibodies are associated with severe pulmonary disease, pulmonary hypertension, severe small bowel involvement, and a poor prognosis. Anti-Th/To antibodies primarily bind to two proteins of the mitochondrial RNA processing (MRP) and the ribonuclease P complexes, are present in 1-13% of SSc patients, and are rarely found in other diseases. Anti-Th/To antibodies are primarily associated with localized cutaneous scleroderma, and associated with pericarditis, interstitial lung disease and a high frequency of “intrinsic pulmonary hypertension, and a poorer prognosis. Autoantibodies to PM/Scl, the human exosome complex, are found in polymyositis/scleroderma overlap syndromes. The majority of anti-PM/Scl reactivity is directed to one of two proteins: PM/Scl100 and/or PM-Scl75.