How Do APLAs Lead to Blood Clots?
We know that APLAs in a test tube cause blood to take a longer than normal time to clot. This is because the antibodies decrease the number of phospholipids available to help the clotting proteins form a clot. On the basis of this information, one would think that people with APLAs would have trouble forming clots (that is, they would have a bleeding disorder). However, APLAs within the body actually cause the opposite reaction and increase the tendency toward clotting. The mechanisms by which APLAs lead to blood clots are not well understood. APLAs may interact with the cells on the inner surface of blood vessels, making them more prone to form clots. They may interact with blood platelets, making them stickier and more likely to cause clots. Moreover, the APLAs may prevent the body s natural ability to break up blood clots by interfering with substances in the blood that normally prevent excessive clotting (protein C and S).
