Lupus and your body

What are antiphospholipid antibodies?

Dr. Michelle Petri is the Director of the Hopkins Lupus Cohort, a longitudinal study of morbidity and mortality in systemic lupus erythematosus, and Co-Director of the Hopkins Lupus Pregnancy Center.

See all of Michelle Petri, MD, MPH's answers.

Antibodies are proteins in the blood that the body produces to fight off foreign agents. Antibodies do this by creating an immunity against unfamiliar microorganisms. Autoantibodies are antibodies that are directed against one’s self.

Antiphospholipid antibodies interfere with the normal function of blood vessels, causing narrowing and irregularity of the vessel (vasculopathy), and by causing blood clots in the vessel (thrombosis). These blood vessel problems can then lead to complications such as stroke, heart attack, and miscarriage.

There are several kinds of antiphospholipid antibodies. The three most widely measured are lupus anticoagulant, anticardiolipin antibody, and anti-β2 glycoprotein I. These antibodies react with proteins in the blood that are bound to phospholipid, a type of fat molecule that is part of the normal cell membrane. Lupus anticoagulant, anticardiolipin antibody and anti-β2 glycoprotein I are closely related, but are not the same antibody. This means that a person can have one and not the others. 

There are other antiphospholipid antibodies, but they are not routinely measured. These include anti-prothrombin, anti-phosphatidylserine, and anti-annexin.

Our thanks to Michelle Petri, MD, MPH, for this information.

Medically reviewed on July 25, 2013