Anti-cardiolipin antibodies

Anti-cardiolipin antibodies (ACA) are antibodies often directed against cardiolipin and found in several diseases including syphilis, antiphospholipid syndrome, livedoid vasculitis, vertebrobasilar insufficiency, Behçet's syndrome , idiopathic spontaneous abortion, and systemic lupus erythematosus(SLE). They are a form of anti-mitochondrial antibody. In SLE, The anti-DNA antibodies and anti-cardiolipin act independently. In rheumatoid arthritis w/systemic sclerosis (scleroderma) 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 ACA are beta-2 glycoprotein independent and can be assayed using the Venereal Disease Research Laboratory test

Apolipoprotein H involvement
β2-glycoprotein I has been identified as Apolipoprotein H 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 are associated with increased thrombosis.