Anti-cardiolipin antibodies (ACA) are antibodies often directed against cardiolipin

Cardiolipin

Cardiolipin is an important component of the inner mitochondrial membrane, where it constitutes about 20% of the total lipid composition. The only other place that cardiolipin can be found is in the membranes of most bacteria. The name ‘cardiolipin’ is derived from the fact that it was first...

 and found in several diseases including syphilis

Syphilis

Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...

, antiphospholipid syndrome

Antiphospholipid syndrome

Antiphospholipid syndrome or antiphospholipid antibody syndrome , often also Hughes syndrome, is an autoimmune, hypercoagulable state caused by antibodies against cell-membrane phospholipids that provokes blood clots in both arteries and veins as well as pregnancy-related complications such as...

, livedoid vasculitis

Livedoid vasculitis

Livedo reticularis is a common cutaneous finding consisting of a mottled reticulated vascular pattern that appears like a lace-like purplish discoloration of the lower extremities. The discoloration is caused by swelling of the medium veins in the skin, which makes them more visible...

, vertebrobasilar insufficiency

Vertebrobasilar insufficiency

Vertebrobasilar insufficiency , or vertebral basilar ischemia , refers to a temporary set of symptoms due to decreased blood flow in the posterior circulation of the brain. The posterior circulation supplies blood to the medulla, cerebellum, pons, midbrain, thalamus, and occipital cortex...

, Behçet's syndrome, idiopathic spontaneous abortion, and systemic lupus erythematosus

Systemic lupus erythematosus

Systemic lupus erythematosus , often abbreviated to SLE or lupus, is a systemic autoimmune disease that can affect any part of the body. As occurs in other autoimmune diseases, the immune system attacks the body's cells and tissue, resulting in inflammation and tissue damage...

(SLE). They are a form of anti-mitochondrial antibody

Anti-mitochondrial antibodies

Anti-mitochondrial antibodies are autoantibodies, consisting of immunoglobulins formed against mitochondria, primarily mitochondria in cells of the liver...

. In SLE, The anti-DNA antibodies and anti-cardiolipin act independently. In rheumatoid arthritis with systemic sclerosis (scleroderma

Scleroderma

Systemic sclerosis or systemic scleroderma is a systemic autoimmune disease or systemic connective tissue disease that is a subtype of scleroderma.-Skin symptoms:...

) these antibodies may tie two conditions together.

Anti-cardiolipin antibodies can be classified in two ways.

• As IgM, IgG or IgA
• As β₂-glycoprotein dependent or independent
  • In autoimmune disease ACA are beta-2 glycoprotein dependent
  • syphilis
    Syphilis
    Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
    
     ACA are beta-2 glycoprotein independent and can be assayed using the Venereal Disease Research Laboratory test
    Venereal Disease Research Laboratory test
    The Venereal Disease Research Laboratory test or VDRL is a blood test for syphilis and was developed by the former Venereal Disease Research Laboratory, now the Treponemal Pathogenesis and Immunology Branch, of the United States Public Health Service...
    
    

Apolipoprotein H involvement

β₂-glycoprotein I has been identified as Apolipoprotein H

Apolipoprotein H

Apolipoprotein H , previously known as , is a multifunctional apolipoprotein. One of its functions is to bind cardiolipin. When bound the structure of cardiolipin and Apo-H both undergo large changes in structure...

 and is required for the recognition of ACA in autoimmune disease. Only a subset of autoimmune anti-cardiolipin antibodies bind Apo-H, these anti-apolipoprotein antibodies

Anti-apolipoprotein antibodies

In autoimmune disease, anti-apolipoprotein H antibodies, also called anti-β2 glycoprotein I antibodies, comprise a subset of anti-cardiolipin antibodies and lupus anticoagulant. These antibodies are involved in sclerosis and are strongly associated with thrombotic forms of lupus....

are associated with increased thrombosis.