Anti–citrullinated protein antibody

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  L-Citrullin
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  Arginin - Arginine

Anti–citrullinated protein antibody

Anti–citrullinated protein antibodies (ACPAs) are a type of autoantibody that target proteins in the body that have undergone a process called citrullination. These antibodies are highly specific for rheumatoid arthritis (RA) and are used as a diagnostic marker for the disease.

Citrullination

Citrullination is a post-translational modification of proteins where the amino acid arginine is converted into citrulline by the enzyme peptidylarginine deiminase (PAD). This process can alter the structure and function of proteins, potentially leading to the generation of neoepitopes that are recognized as foreign by the immune system.

Role in Rheumatoid Arthritis

In rheumatoid arthritis, the presence of ACPAs is associated with more severe disease and can be detected years before the onset of clinical symptoms. The presence of these antibodies is considered a hallmark of the disease and is included in the American College of Rheumatology/European League Against Rheumatism classification criteria for RA.

Diagnostic Use

ACPAs are detected using enzyme-linked immunosorbent assay (ELISA) tests, which measure the level of these antibodies in the blood. The most common test for ACPAs is the anti-cyclic citrullinated peptide (anti-CCP) test. A positive anti-CCP test is highly specific for rheumatoid arthritis and can help differentiate it from other forms of arthritis.

Pathogenesis

The exact role of ACPAs in the pathogenesis of rheumatoid arthritis is not fully understood. However, it is believed that these antibodies contribute to the inflammatory process by forming immune complexes that activate the complement system and recruit inflammatory cells to the joints. This leads to the characteristic joint inflammation and damage seen in RA.

Treatment Implications

The presence of ACPAs in patients with rheumatoid arthritis can influence treatment decisions. Patients with ACPA-positive RA may have a more aggressive disease course and may require more intensive treatment strategies, including the use of disease-modifying antirheumatic drugs (DMARDs) and biologic agents.

Related pages

• Rheumatoid arthritis
• Autoantibody
• Citrullination
• Enzyme-linked immunosorbent assay

Rheumatologic diseases

Arthritis is often used to refer to any disorder that affects the joints. Rheumatic diseases usually affect joints, tendons, ligaments, bones, and muscles. Rheumatologic diseases usually affect joints, tendons, ligaments, bones, and muscles.

Connective Tissue Diseases

Rheumatology and	Connective Tissue Diseases
Ankylosing spondylitis	Arthritis
Arthritis and Rheumatic diseases	Autoimmune diseases
Autoinflammatory diseases	Behçet’s disease
Bursitis	Giant cell arteritis
Gout	Juvenile arthritis
Knee problems	Lupus
Osteoarthritis	Polymyalgia rheumatica
Psoriatic arthritis	Reactive arthritis
Rheumatoid arthritis	Scleroderma
Sjögren’s syndrome	Systemic lupus erythematosus (Lupus)
Tendinitis	Rheumatologic diseases