The Annexin V IgM antibodies test is a specialized immunoassay designed to detect the presence of IgM class autoantibodies directed against annexin V, a calcium-dependent phospholipid-binding protein involved in crucial physiological processes such as apoptosis and blood coagulation. This test is utilized in the investigation of thrombotic disorders, autoimmune conditions, and recurrent pregnancy loss.
Annexin V binds to phosphatidylserine exposed on the outer membrane of apoptotic cells, effectively masking these procoagulant surfaces and preventing inappropriate activation of the clotting process. This anticoagulant property of annexin V is crucial for maintaining vascular stability and avoiding excessive coagulation. When IgM autoantibodies against annexin V are present, they can bind to the protein and neutralize its function, leading to the exposure of anionic phospholipids and increased thrombin production. The loss of anticoagulant protection then promotes a prothrombotic environment, which may result in deep vein thrombosis, stroke, or other vascular problems.
Annexin V IgM antibodies have been identified in some patients with antiphospholipid syndrome (APS), an autoimmune disorder characterized by recurrent arterial or venous blood clots and pregnancy complications associated with antiphospholipid antibodies. While anti-β2 glycoprotein I and lupus anticoagulant are the main markers for APS, anti-annexin V antibodies, including the IgM type, are increasingly seen as an additional risk factor. Detecting these antibodies can help identify seronegative cases or patients with unusual clinical signs. Additionally, higher levels of annexin V IgM have been observed in systemic lupus erythematosus (SLE) and other systemic autoimmune diseases, where they may play a role in vascular inflammation and damage to the blood vessel lining.
