Anti-citrullinated protein antibodies

Anti-citrullinated Protein Antibodies

Anti-citrullinated protein antibodies (ACPAs) are a type of autoantibody frequently associated with rheumatoid arthritis (RA). These antibodies target proteins that have undergone a post-translational modification known as citrullination, where the amino acid arginine is converted into citrulline. The presence of ACPAs is a significant marker in the diagnosis and prognosis of RA.

Background

Citrullination is a normal physiological process that occurs during inflammation and apoptosis. However, in certain individuals, the immune system mistakenly identifies citrullinated proteins as foreign, leading to the production of ACPAs. These antibodies are highly specific for rheumatoid arthritis and can be detected in the blood of patients years before the onset of clinical symptoms.

Clinical Significance

ACPAs are considered one of the most specific biomarkers for rheumatoid arthritis. They are present in approximately 60-80% of patients with RA and are rarely found in healthy individuals or those with other diseases. The presence of ACPAs is associated with a more aggressive disease course and can predict the development of joint damage.

Detection

ACPAs are typically detected using an enzyme-linked immunosorbent assay (ELISA). The most common test for ACPAs is the anti-cyclic citrullinated peptide (anti-CCP) test, which has a high specificity for RA. The detection of ACPAs is often used in conjunction with other diagnostic criteria, such as the presence of rheumatoid factor (RF) and clinical symptoms, to diagnose RA.

Pathogenesis

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

Treatment Implications

The presence of ACPAs can influence treatment decisions in RA. Patients with ACPA-positive RA may benefit from more aggressive treatment strategies to prevent joint damage. Disease-modifying antirheumatic drugs (DMARDs) and biologic agents are commonly used to manage RA and reduce the impact of ACPAs on disease progression.

Also see

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

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