Anti–citrullinated protein antibody

Anti–citrullinated protein antibody (ACPA) is a type of antibody that is produced by the immune system in response to citrullinated proteins. These antibodies are commonly found in the blood of individuals with certain autoimmune diseases, most notably rheumatoid arthritis.

Overview

Citrullination is a process that occurs naturally in the body, where the amino acid arginine in a protein is converted into the amino acid citrulline. This process can alter the structure and function of the protein. In some individuals, the immune system recognizes these citrullinated proteins as foreign and produces antibodies against them, known as ACPAs.

Role in Rheumatoid Arthritis

ACPA is particularly associated with rheumatoid arthritis (RA), a chronic inflammatory disorder that primarily affects the joints. It is estimated that up to 80% of individuals with RA have detectable levels of ACPA in their blood. The presence of ACPA in the blood is one of the criteria used for the diagnosis of RA.

Detection and Diagnosis

ACPA can be detected in the blood using a specific blood test known as the anti-CCP (cyclic citrullinated peptide) test. This test is often used in conjunction with other tests, such as the rheumatoid factor test, to diagnose RA.

Clinical Significance

The presence of ACPA in the blood is not only a diagnostic marker for RA, but it is also associated with a more severe disease course. Individuals with ACPA-positive RA are more likely to have erosive joint disease and are less likely to achieve remission with treatment.

Research and Future Directions

Research is ongoing to better understand the role of ACPA in the pathogenesis of RA and other autoimmune diseases. There is also interest in developing therapies that can specifically target ACPA in order to treat these diseases.