Detection of
autoantibodies
An autoantibody is an antibody (a type of protein) produced by the immune system that is directed against one or more of the individual's own proteins. Many autoimmune diseases (notably lupus erythematosus) are associated with such antibodies.
Pr ...
against mutated citrullinated vimentin is part of
rheumatoid arthritis (RA) diagnostics, especially in sera negative for
rheumatoid factor
Rheumatoid factor (RF) is the autoantibody that was first found in rheumatoid arthritis. It is defined as an antibody against the Fc portion of IgG and different RFs can recognize different parts of the IgG-Fc. RF and IgG join to form immune com ...
(RF negative sera). Anti-MCV antibodies are a member of the
ACPA family, a group of the so-called antibodies to citrullinated protein/peptide antigens.
Rheumatoid arthritis is an
autoimmune disorder. Detection of specific autoantibodies (antibodies directed against the body’s own tissue) such as rheumatoid factors and ACPAs may provide indication of the disease. In many cases, autoimmune diagnostics are crucial for diagnosing RA correctly and already in the disease’s early stages, when typical symptoms often are lacking but when medical therapy is most effective.
Basics
Citrullination
Citrullination or deimination is the conversion of the amino acid arginine in a protein into the amino acid citrulline. Citrulline is not one of the 20 standard amino acids encoded by DNA in the genetic code. Instead, it is the result of a post-tr ...
is a modification of proteins where a
nitrogen in the
amino acid arginine
Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) and both the am ...
is
replaced with an
oxygen, converting it into
citrulline. The modified (citrullinated) protein may be identified by as foreign, provoking an autoimmune inflammation response.
Various kinds of citrullinated proteins have been detected in the joints of RA patients. One of these is Sa antigen, now known as mutated citrullinated vimentin (MCV).
Citrullination of
vimentin plays a decisive role in RA pathogenesis.
Significance
In rheumatology diagnostics, autoantibodies against mutated citrullinated vimentin (anti-MCV) are of prominent diagnostic and prognostic value. Their significance is greater than that of rheumatoid factor.
Recently a serological
point-of-care test (POCT) for the early detection of RA has been developed. This assay combines the detection of rheumatoid factor and anti-MCV for diagnosis of rheumatoid arthritis and shows a sensitivity of 72% and specificity of 99.7%.
Anti-MCV are used as efficient
biomarkers for estimating progress of rheumatoid arthritis. Main advantage of testing for anti-MCV is the early appearance of the anti-MCV antibodies, what allows for detection of early RA and submits adequate therapy just after the disease’s onset. Moreover, anti-MCV titres show strong correlation to disease activity, disease severity and the success of therapy.
References
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Arthritis