Antiphospholipid Antibodies (APA)

Repeated miscarriage and implantation failure may be caused in part by antiphospholipid antibodies. Antiphospholipid antibodies form against a group of fatty molecules located in the outer membrane of the cell known as phospholipids.  There are a number of different phospholipids that that serve different roles.  Some phospholipids normally face inward into the cell and, therefore, are not normally visible to the environment outside the cell.  During certain cellular events, these phospholipids can shift their position facing outward where they can then interact with molecules external to the cell.  There, they can participate in a number of different important cellular events involving other cells and proteins.  Some of these interactions are with members of the blood clotting cascade.  The orchestration of these events is delicately balanced in the normal individual.

Under certain abnormal conditions, unusually high quantities of antibodies can form directed against the phospholipids or related proteins. When this occurs, abnormalities in coagulation can be expected. Well-known complications may follow.  These may include an increased risk of forming blood clots as well as pregnancy complications such as miscarriage, preterm labor and restricted fetal growth.  Futhermore, because the placenta differs from other tissues in the body it is even more vulnerable to damage from antiphospholipid antibodies.  Unlike other cells of the body that only rarely place phospholipids on their surfaces, placental cells place phospholipids on the surfaces at all times. This exposes the placenta to antibodies if they are present.  There, the phospholipids participate in formation of the cellular surface of the placental villi (finger-like projections of fetal tissue that exchange nutrients and oxygen with the mothers blood). The outcome may be poor implantation, resulting in infertility or pregnancy loss.

Testing for antiphospholipid antibodies is important in patients who suffer recurrent miscarriage and unexplained infertility.  There are numerous potential phospholipids and proteins that antibodies can form against.  We perform tests on those that we regard as most significant.  (J.A.McIntyre, Antiphospholipid Antibodies and Implantation Failure, AJRI (2003) 49:221-229)  Treatment of Antiphospholipid Antibody Syndrome often consists of baby aspirin and heparin or Lovenox, often in combination with IVIG.  Together these treatments may  work together to diminish the clotting tendency as well as to decrease inflammation.

Certain phospholipids are present under normal conditions on the outer surface of the placental cell (known as the syncytiotrophoblast).  These important cells are formed from their parent placental cells (known as cytotrophoblast) in the presence of the phospholipids displayed on the outer cell surface.  These phospholipids permit the joining together (fusion) of the cytotrophoblast into the syncytiotrophoblast.  The mature syncytiotrophoblast functions to produce placental hormones and to transfer nutrients to the baby. Antiphospholipid antibodies often prevent cell fusion and disrupt placental function.