Anti-citrullinated protein antibody

Anti-citrullinated protein antibody

Anti-citrullinated protein antibodies (ACPAs) are a type of autoantibody frequently detected in the blood of patients 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 highly specific for RA and is used as a diagnostic marker for the disease.

Background

Citrullination is a normal physiological process that occurs during inflammation and cell death. However, in individuals with rheumatoid arthritis, the immune system mistakenly identifies citrullinated proteins as foreign, leading to the production of ACPAs. These antibodies contribute to the inflammatory processes that characterize RA, resulting in joint damage and other systemic symptoms.

Diagnostic Significance

ACPAs are detected using various laboratory techniques, most commonly the enzyme-linked immunosorbent assay (ELISA). The presence of ACPAs is considered a hallmark of RA, with a specificity of approximately 95%. This means that while not all patients with RA will have ACPAs, those who do are very likely to have the disease. The detection of ACPAs can precede the clinical onset of RA by several years, making them valuable for early diagnosis and intervention.

Pathophysiology

The exact role of ACPAs in the pathogenesis of RA is not fully understood, but they are believed to contribute to the disease process by:

• Promoting the formation of immune complexes that deposit in the joints, leading to inflammation.
• Activating complement pathways, which further exacerbate inflammatory responses.
• Interacting with other immune cells, such as macrophages and T cells, to perpetuate the autoimmune response.

Clinical Implications

The presence of ACPAs is associated with a more severe disease course in RA, including:

• Increased risk of joint erosions and deformities.
• Higher likelihood of extra-articular manifestations, such as rheumatoid nodules and vasculitis.
• Greater need for aggressive treatment strategies, including disease-modifying antirheumatic drugs (DMARDs) and biologic agents.

Also see

• Rheumatoid arthritis
• Autoantibody
• Citrullination
• Enzyme-linked immunosorbent assay
• Disease-modifying antirheumatic drugs

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