APS 101, a new series created by the Jason Knight Lab, will take you through the ins and outs of APS, providing facts and key information to help you better understand the disease.
APS 101 is written by Jacqueline Madison, MD, Assistant Professor in the Division of Rheumatology and member of the Jason Knight Lab. In this first edition, Dr. Madison explains antiphospholipid antibodies and phospholipids.
Antiphospholipid Antibodies and Phospholipids
A diagnosis of APS (antiphospholipid syndrome) brings up a lot of questions, so let’s start with the basics.
Antiphospholipid Antibodies
What is an antiphospholipid antibody? It’s in the name of the diagnosis, so let's start there. APS is an autoimmune disease, meaning that the body’s immune system, which normally fights infections and cancers, loses control and starts attacking the person’s own body.
For example, rather than making antibodies that recognize and help our white blood cells kill infectious particles (like bacteria or viruses), autoimmune white blood cells accidentally make antibodies that recognize parts of the body. Different autoantibodies identify different targets, which leads to the wide variety of symptoms we see across the whole spectrum of autoimmune diseases.
In APS, the immune system makes antibodies against a substance called phospholipids. In science and medicine, we can use "anti-" to mean “against” which in this case is kind of like “recognizes.” It does not mean “against” as in the antibodies are mad at the phospholipids (probably antibodies don’t have strong feelings like that, although I guess I’ve never asked them!). So “antiphospholipid” just means that we are talking about an antibody that recognizes a phospholipid and can attach itself to it.
Phospholipids
So, what is a phospholipid!? That’s a long word you don’t hear every day (unless you work in the Knight Lab). Lipid is another word for fat. There are different types of lipids in the body. Lipids are not only what you might typically think of as fat, such as cholesterol; lipids can also play important roles as building blocks of our cells.
You may recall from biology class that the cell membranes of all animal cells are made from two layers of a special type of lipid called “phospholipids.” These membrane layers keep the cell contents (like the nucleus) inside the cell and everything else (like bacteria) outside the cell. So, antiphospholipid antibodies tend to interact with and damage these cell membranes.
In APS, there is not just one type of antiphospholipid antibody, but several! To complicate matters further, some of the so-called “antiphospholipid” antibodies don’t actually interact with phospholipids directly, but instead interact with other protein molecules that are in close association with the phospholipids [1]. So tricky! For example, anticardiolipin antibodies recognize a phospholipid called cardiolipin, but anti-beta-2-glycoprotein I antibodies recognize one of those phospholipid-associated proteins [2, 3].
There is ongoing research, including in our lab, to better identify and understand all the antiphospholipid antibodies that are important in APS. We hope that by completely understanding the whole pattern of positive antibodies in an individual, we will eventually be able to offer more proactive and personalized types of treatments.
Contributed by Jacqueline Madison, MD
References:
- Vreede, A.P., P.L. Bockenstedt, and J.S. Knight, Antiphospholipid syndrome: an update for clinicians and scientists. Curr Opin Rheumatol, 2017. 29(5): p. 458-466.
- McNeil, H.P., C.N. Chesterman, and S.A. Krilis, Binding specificity of lupus anticoagulants and anticardiolipin antibodies. Thromb Res, 1988. 52(6): p. 609-19.
- Roubey, R.A., et al., Lupus anticoagulant activity of autoimmune antiphospholipid antibodies is dependent upon beta 2-glycoprotein I. J Clin Invest, 1992. 90(3): p. 1100-4.
Join Our Email List
If you are interested in receiving updates on our patient care and research efforts, please join our APS Program email list. Read the APS Program August 2021 Update.
