Antiphospholipid Antibodies
What are antibodies?
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.
What are autoantibodies?
Autoantibodies are antibodies that are directed against one's self.
What are antiphospholipid antibodies?
Antiphospholipid antibodies interfere with the normal function of blood vessels. They typically cause two kinds of problems:
- narrowing and irregularity of the blood vessels (vasculopathy)
- blood clots in the blood vessel (thrombosis).
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. These blood vessel problems can then lead to complications such as stroke, heart attack, and miscarriage.
There are several kinds of antiphospholipid antibodies. The two most commonly measured kinds are:
- lupus anticoagulant
- anticardiolipin antibody
Lupus anticoagulant and anticardiolipin antibody are closely related, but are not the same antibody. This means that a person can have one and not the other. For example, in various studies, 8 percent to 65 percent of people with lupus have the lupus anticoagulant, and 25 percent to 61 percent have anticardiolipin antibody. These antibodies can also be found in people who do not have lupus.
There are other antiphospholipid antibodies, but they are not routinely measured. These include:
- anti-beta 2 glycoprotein 1
- anti-prothrombin
- the "false-positive" test for syphilis
How common are antiphospholipid antibodies?
Like other autoantibodies in systemic lupus, antiphospholipid antibodies can come and go in an individual. There are many ways to measure these antibodies, and different methods may not always give the same result.
These antibodies were first discovered in people who have lupus, but it is not necessary to have lupus to have these antibodies. In fact, in most studies, more than 50 percent of people with these antibodies do not have lupus. We do not yet understand why a person's immune system begins to manufacture these antibodies.